# ASD-STE100 Writing Rules — Complete Reference

**Source:** ASD-STE100 Simplified Technical English, Issue 9 (2025-01-15), Part 1 — Writing rules.
**Structure:** 9 sections containing 53 numbered rules (Section 1: 14, Section 2: 2, Section 3: 7, Section 4: 5, Section 5: 5, Section 6: 6, Section 7: 3, Section 8: 7, Section 9: 4), plus 8 General recommendations (GR-1..GR-8) in Section 9 that are explicitly NOT STE rules.
**Conventions in this file:** each rule gives the normative statement (numeric limits verbatim from the spec), condensed details/exceptions, and one Non-STE → STE example pair. Sentence-length limits at a glance: procedures max 20 words (5.1), descriptive text max 25 words (6.3), note sentences max 25 words (5.5), paragraphs max 6 sentences (6.6).

---

## Section 1 - Words

Governs which words you can use: approved dictionary words (used only as their approved part of speech, meaning, and form), plus technical nouns and technical verbs from 22 and 4 categories respectively. "Subject fields" follows ISO 1087:2019.

### Rule 1.1 - Use words that are: Approved in the dictionary, Technical nouns, Technical verbs.
STE has a controlled dictionary (Part 2) of the words most frequently used in technical writing. You can also use words NOT in the dictionary if you can include them in the specified categories of technical nouns (Rule 1.5) and technical verbs (Rule 1.12). A technical noun is a noun term that refers to a specified concept and is applicable to a subject field; a technical verb is a verb term that refers to a specified concept or process and is applicable to a subject field. Technical nouns/verbs usually live in your company glossary or terminology database.
- Examples: "use" is an approved verb in the dictionary; "engine" is a technical noun; "ream" is a technical verb.

### Rule 1.2 - Use approved words from the dictionary only as the specified part of speech.
Some words are approved as more than one part of speech (e.g. "clean" = verb and adjective). If the approved alternative for an unapproved word has a different part of speech, you must change the sentence construction; a word-for-word replacement is possible only when parts of speech match.
- Non-STE: "Make sure that the valve is operable." → STE: "Make sure that the valve can operate." ("Operable" is unapproved; the alternative "operate" is a verb, so the construction changes.)

### Rule 1.3 - Use approved words only with their approved meanings.
Each approved word has a specified approved meaning, often more restricted than in standard English.
- Non-STE: "Follow the safety instructions." → STE: "Obey the safety instructions." ("Follow" is approved only as "come after, go after.")

### Rule 1.4 - Use only the approved forms of verbs and adjectives.
The dictionary lists each approved verb with its approved forms, and adjectives with comparative/superlative forms where applicable (forms made with "more"/"most" are not listed because those words are approved).
- Example: dictionary entry `REMOVE (v), REMOVES, REMOVED, REMOVED` gives infinitive/imperative "(to) remove," simple present "remove(s)," simple past "removed," past participle (as adjective) "removed." Entry `SLOW (adj) (SLOWER, SLOWEST)` gives base, comparative, superlative.

### Rule 1.5 - You can use words that you can include in a technical noun category.
The dictionary does NOT include technical nouns (too many; each subject field differs). You can use technical nouns in procedural and descriptive writing if you can include them in one or more of these twenty-two (22) categories (example words below are illustrative, not a full list):
1. **Official parts information** — bolt, cable, engine, oil seal, transceiver
2. **Vehicles or machines, and locations on them** — aircraft, cargo compartment, cockpit, fuselage, wing root
3. **Tools and support equipment, their parts, and locations on them** — clamp, drill, gauge (gage), test rig, torque wrench
4. **Materials, consumables, and unwanted material** — adhesive, debris, fuel, grease, sealant
5. **Facilities, infrastructure, and logistic procedures** — airport, hangar, packaging, shipping, storage
6. **Systems, components and circuits, their functions, configurations, and parts** — air conditioning, exhaust, pump, reverse mode, standby mode
7. **Mathematical, scientific, engineering terms, and formulas** — acceleration, coefficient, resistance, torque, "C = (A - B) - 0.063 mm"
8. **Navigation and geographic terms** — altitude, coordinates, glideslope, heading, north
9. **Numbers, units of measurement and time (and their symbols)** — 92, degree (°), kilogram (kg), ohm (Ω), second (″)
10. **Quoted text** (texts you cannot change: placards, labels, signs, markings, display units) — EXIT sign, ON position, FAULT legend, NO STEP marking
11. **Professional roles, individuals, groups, organizations, and geopolitical entities** — captain, crew chief, Federal Aviation Administration (FAA), manufacturer, United States of America (USA)
12. **Parts of the body** — blood, ear, lung, respiratory tract, skin
13. **Common personal effects, food, and beverages** — clothing, coffee, footwear, jewelry, matches
14. **Medical terms** — allergy, dizziness, irritation, nausea, pulse
15. **Official documents, parts of documentation, standards, and guidelines** — chapter, data module, figure, Service Bulletin, Structural Repair Manual
16. **Environmental and operational conditions** — humidity, ice, lightning, turbulence, volcanic ash
17. **Colors** — beige, black, gray, magenta, red. NOTE: colors are adjectives, but STE identifies them as technical nouns; comparative and superlative forms of colors (e.g. blacker, the reddest) are NOT permitted in STE.
18. **Damage terms** — corrosion, crack, dent, distortion, scratch
19. **Computer science, information and communication technology** — artificial intelligence, cursor, database, firewall, touchscreen
20. **Civil and military operations** — checkpoint, deployment, mission, Original Equipment Manufacturer (OEM), patrol
21. **Law and regulations** — arbitration, compliance, contract, jurisdiction, waiver
22. **Animals, plants, and other life forms** — bacteria, bird, fungi, insect, termite

### Rule 1.6 - Use a word that is not approved in the dictionary, only when it is a technical noun or part of a technical noun.
The same word can go into different categories with different meanings in different contexts. A word not in the dictionary at all can still be used if it is part of a technical noun (e.g. "relative" in "relative angular position").
- Non-STE: "Make sure that the two spigots at the base of the unit engage." → STE: "...at the bottom of the unit engage." But STE: "The base of the triangle is 5 cm." ("Base" is unapproved for a surface, yet valid as a technical noun in category 7.)

### Rule 1.7 - Do not use words that are technical nouns as verbs.
Use a technical noun only as a noun, or as an adjective in a different technical noun. Some words can be both a technical noun AND a technical verb when they fit a category of each (e.g. "drill").
- Non-STE: "Oil the steel surfaces." → STE: "Apply oil to the steel surfaces."

### Rule 1.8 - Use technical nouns that are approved in your company, industry, or subject field.
If an approved technical noun exists for a system, component, part, or process (usually in official parts information and company documentation), use it.
- STE: "The front panel of the phone has a touchscreen and a home button." ("Touchscreen" and "home button" are approved in the subject field.)

### Rule 1.9 - When you must select a technical noun, use one which is short and easy to understand.
When no technical noun is already approved, select one that is short (not more than three words) and easy to understand. With index numbers and a clear illustration, a short noun alone is sufficient.
- Non-STE: "Remove the four stainless steel pan head machine screws (10) that attach the metallic machined flange (15) to the front housing cover (20)." → STE: "Remove the four screws (10) that attach the flange (15) to the cover (20)."

### Rule 1.10 - Do not use regional, slang, or jargon words as technical nouns.
Words understood only in some regions or by small groups cause confusion; always use well-known words.
- Non-STE: "After the firmware update, do not brick the router." → STE: "After the firmware update, do not set the router to OFF." ("Brick" is IT slang.)

### Rule 1.11 - Do not use different technical nouns for the same item.
Select the technical noun approved in your company/industry/subject field and use it consistently throughout the text.
- Non-STE: steps that call the same item "servo control unit," "actuator," and "control unit" → STE: use "actuator" in all three steps ("Make sure that the actuator is in the open position." / "Do the operational test of the actuator." / "Disconnect the actuator from the test rig.").

### Rule 1.12 - You can use verbs that you can include in a technical verb category.
The dictionary does NOT include technical verbs. Technical verbs must obey the same rules as other approved verbs (Section 3). Prefer approved dictionary verbs first: do not use a technical verb if you can write the same sentence with approved dictionary words (if possible, use an approved verb + an applicable technical noun). You can use technical verbs in procedural and descriptive texts if you can include them in one or more of these four (4) categories:
1. **Manufacturing processes** — terms that give instructions/information to:
   - a) Remove material: drill, grind, mill, ream, unsolder
   - b) Add material: flame, insulate, remetal, retread
   - c) Attach material: braze, crimp, solder, weld
   - d) Change the mechanical strength, the structure, or the physical properties of a material: anneal, cure, freeze, heat-treat, magnetize
   - e) Change the surface finish of a material: buff, burnish, passivate, plate, polish
   - f) Change the shape of a material: blend, cast, extrude, spin, stamp
2. **Computer processes and applications** — terms that give instructions/information for:
   - a) Input and output processes: click, digitize, enter, swipe, type
   - b) User interface and application processes: copy, delete, drag and drop, paste, scroll, zoom in
   - c) System operations: boot, debug, download, install, reboot, upgrade
3. **Instructions and information for applicable subject fields** — terms in these contexts:
   - a) Engineering, mathematical, and scientific: bisect, compensate for, convert, modulate, radiate
   - b) Medical: disinfect, intubate, prescribe, sanitize, sterilize
   - c) Civil and military operations: aim, arm, fire, intercept, unlatch
   - d) Navigation: approach, descend, hover, land, taxi
   - e) Automotive and railway: accelerate, brake, couple, inflate, steer
   - f) Energy, oil, and gas: compress, distill, extract, inject, pump
4. **Law and regulations** — terms that give instructions/information ONLY for legal and regulatory texts (contracts, warranty texts, certificates, standards and specifications, legal papers): acknowledge, comply with, enforce, notify, supersede, waive
- Non-STE: "If you detect broken wires, repair them." → STE: "If you find broken wires, repair them." (approved verb suffices) But STE: "The security scanner detects metal objects." ("Detect" is the correct technical verb in that context.)

### Rule 1.13 - Do not use technical verbs as nouns.
Use technical verbs only as verbs. Exception: you can use the past participle form of technical verbs as adjectives (e.g. "Lubricate the reamed hole."). Some words can be both technical verb and technical noun when they fit a category of each (e.g. "plate").
- Non-STE: "Give the hole 0.20-inch ream." → STE: "Ream the hole to a 0.20-inch dimension."

### Rule 1.14 - Use American English spelling unless other official directives tell you differently.
Use the spelling of the STE dictionary (American English, per Merriam-Webster). Exception: keep quoted text as it is, even with British spelling (refer to Rule 8.6).
- Non-STE: "Change the colour of the display." → STE: "Change the color of the display."

---

## Section 2 - Multi-word nouns

Groups of nouns/adjectives that work as one part of speech ("multi-word nouns") are hard to parse when long; the head noun is usually the last word.

### Rule 2.1 - Write multi-word nouns of no more than three words.
Keep multi-word nouns to a maximum of three words. To keep them short, use prepositions (for example, "of," "on," "in," "for") and explain the multi-word nouns.
- Non-STE: "Runway light connection resistance calibration." (5 words) → STE: "Calibration of the resistance of the runway light connection." (1 word, 1 word, and 3 words)

### Rule 2.2 - When a technical noun has more than three words, write it in full. Then, you can use one of these methods to make the technical noun clear: give a shorter form of the technical noun; or use hyphens (-) between words that you use as one unit.
Method 1 (shorter form): write the official long technical noun in full the first time, then use a shorter form or an approved abbreviation (e.g. "ramp service door safety connector pin" → "safety connector pin"). If a technical noun has three words or less, abbreviations are not necessary. Method 2 (hyphens): hyphenate the words that operate as one unit; hyphenated words always count as one word. Do not use hyphens to make groups of more than three words, do not connect unrelated words, and never remove a hyphen that is part of an approved technical noun (e.g. "inward-outward valve").
- Non-STE: "Move the main-gear-door-retraction-winch handle." (all one hyphen group) → STE: "Move the main-gear-door retraction-winch handle." (3 words)

---

## Section 3 - Verbs

Restricts verb forms and tenses, bans complex constructions and most "-ing" forms, and requires the active voice.

### Rule 3.1 - Use only the verb forms that are given in the dictionary.
The dictionary gives the verb forms you can use for each approved verb, e.g. REMOVE (v) — REMOVES, REMOVED, REMOVED; GIVE (v) — GIVES, GAVE, GIVEN. The dictionary introduction (Part 2) explains the four verb types (regular, irregular, irregular auxiliary, defective modal).

### Rule 3.2 - Use only these verb forms and tenses of verbs: the infinitive form; the imperative form (command form); the simple present tense; the simple past tense; the simple future tense; the past participle form (as an adjective).
For "(to) adjust": infinitive "(to) adjust"; imperative "adjust + object"; simple present "adjust(s)"; simple past "adjusted"; simple future "will adjust"; past participle as adjective "the adjusted linkage."
- Not approved: the present perfect ("has adjusted"), the past perfect ("had adjusted"), the progressive forms ("is/was adjusting"), and all other complex verb constructions.

### Rule 3.3 - Use the past participle form as an adjective.
The past participle as an adjective shows the condition of something — this is NOT passive voice. Use it before a noun, or after a form of "to be," "to become," or "to stay." Some dictionary adjectives are past participles of unapproved verbs (e.g. "permitted," "damaged") and are usable as adjectives.
- STE: "Examine all parts of the disassembled unit for damage." / STE: "Make sure that the mating surfaces are not damaged."

### Rule 3.4 - Do not use auxiliary verbs to make complex verb constructions.
Do not combine auxiliaries ("have," "be," modals) with the past participle as a verb: that makes unapproved tenses or passive constructions.
- Non-STE: "The operator has adjusted the linkage." → STE: "The operator adjusted the linkage."

### Rule 3.5 - Use the "-ing" form of a verb only as a technical noun or as a modifier in a technical noun.
"-ing" words have many functions in English and cause ambiguity, so they are usually not permitted. Permitted: as a technical noun (e.g. titles/headings: Cleaning, Troubleshooting) or as a modifier in a technical noun (air-conditioning system, grinding wheel, welding torch). The dictionary approves only a few "-ing" words: nouns lighting, opening, routing, servicing; adjectives mating, missing, remaining; pronoun something; preposition during.
- Non-STE: "When you are doing this procedure, obey all the safety precautions." → STE: "When you do this procedure, obey all the safety precautions."

### Rule 3.6 - Use the active voice. In descriptive writing, you can use the passive voice only if the agent is unknown.
Test for passive: ask "by whom or by what?" — if the text answers it, the sentence is passive. Four methods to change passive to active: (1) put the agent (object of "by") at the start as the subject — the diagram shows "[The main gear leg] [is held by] [the side stay]" inverting to "[The side stay] [holds] [the main gear leg]"; (2) change an infinitive verb to an active verb; (3) in procedural writing, change the verb to the imperative form ("The test can be continued by the operator." → "Continue the test."); (4) when no agent is given, use "you" (the reader) or "we" (your company) as subject. When the agent is truly unknown, passive is correct in descriptive writing ("During transmission, the data was corrupted.") or use "something" as agent.
- Non-STE: "The circuits are connected by a switching relay." → STE: "A switching relay connects the circuits."

### Rule 3.7 - Use an approved verb to describe an action, not a noun or other parts of speech.
Verbs describe actions more clearly than nouns. If a word is not approved as a verb, do not use it as a verb — use a different construction ("check" is a noun: "Do a check of the laptop battery.").
- Do not write: "The ohmmeter gives an indication of 450 ohms." → WRITE: "The ohmmeter shows 450 ohms." (Both sentences are STE, but the sentence with the direct verb describes the action more clearly.)

---

## Section 4 - Sentences

General sentence rules applicable to both procedures (Section 5) and descriptive text (Section 6): short clear sentences, no omitted words, vertical lists, connectors, articles.

### Rule 4.1 - Write short and clear sentences.
In procedures, give short and clear instructions directly to the reader (imperative form). In descriptive text, give each sentence only one topic, without the imperative. Never be abstract: show clearly how to do the task or how the system operates.
- Do not write: "No leaks are permitted." → WRITE: "Make sure that there are no leaks."

### Rule 4.2 - Do not omit words or use contractions to make your sentences shorter.
Each sentence must have all its parts. Do not omit nouns, verbs, subjects, or articles, and do not use contractions ("don't," "isn't"): shorter is not easier to read.
- Non-STE: "If installed, remove the shims." → STE: "If shims are installed, remove them."

### Rule 4.3 - Use a vertical list for complex text.
When a sentence must include many items or actions, put them in a vertical list. Put a colon (:) at the end of the lead-in; identify each item with a number, letter, punctuation mark, or symbol (for example a dash, bullet point, letter, or number); start each item with an uppercase letter; where applicable, use an article before the noun that is the subject of each item; put a period after an item only if it is a full sentence, none otherwise (never a comma or semicolon); put a period at the end of the last item. Do not mix procedural and descriptive writing in one list; in safety instructions repeat negative commands (DO NOT) per item; keep all items at the same level (no nested lists — flatten with parentheses); make sure every item connects correctly to the lead-in.
- Non-STE: "The wheel assembly comprises the tire, the tube, the spokes, the spoke fittings, the valve, and the hub." → STE: "The wheel assembly has these parts:" followed by dash items "- The tire / - The tube / - The spokes / - The spoke fittings / - The valve / - The hub." (period only on the last item)

### Rule 4.4 - Use connecting words and connecting phrases to connect sentences that contain related topics.
Approved connecting words include "and," "but," "then," "thus"; connecting phrases include "as a result," "at the same time." Demonstrative adjectives can also connect related sentences. In procedures, use them when an explanation is necessary after a work step; they can also make safety instructions clearer.
- STE: "When the hydraulic pressure is released, the sequence valve moves to the open position. As a result, the actuators are connected to the hydraulic return."

### Rule 4.5 - When applicable, use an article (the, a, an) or a demonstrative adjective (this, these) before a noun or a multi-word noun.
Do not omit articles/demonstratives to shorten text. Do not use articles in general statements or concepts ("Solvents can cause damage to paint."). In a series of items, article placement changes meaning: "Install the new O-rings (15), spacers (14), nut (13), and safety pin (12)." = all items are new; "Install the new O-rings (15), the spacers (14), the nut (13), and the safety pin (12)." = only the O-rings are new. No definite article before a noun with an alphanumeric identifier ("Tag circuit breaker 36L7.", not "Tag the circuit breaker 36L7.").
- Non-STE: "Data module tells you how to operate unit." → STE: "This data module tells you how to operate the unit."

---

## Section 5 - Procedural writing

Procedures give instructions that tell the reader how to do a task: short imperative sentences, one instruction per sentence, conditions first, notes for information only.

### Rule 5.1 - Write short sentences. Use a maximum of 20 words in each sentence.
The 20-word maximum applies to every procedural sentence, including warnings, cautions, and other safety instructions. Divide a long instruction into two shorter sentences when the actions occur at the same time and cannot become separate work steps. (Notes are the exception: maximum 25 words per sentence — see Rule 5.5. Word-count rules are in Section 8.)
- Non-STE: "Put preservation oil into the unit through the vent hole until the oil level is approximately 6 mm (0.24 inches) below the surface of the flange cover." (25 words) → STE: "Put preservation oil into the unit through the vent hole." (10 words) "Continue until the oil level is approximately 6 mm (0.24 in) below the surface of the flange cover." (16 words)

### Rule 5.2 - Write only one instruction in each sentence unless two or more actions occur at the same time.
Show the sequence of work steps with numbers or letters. One sentence may hold multiple instructions only when the actions occur at the same time ("Hold the panel in its open position and install the fastener."). A work step may hold more than one sentence when actions are simultaneous or a result/limit immediately follows the action ("Measure the leakage from the outlet port. The leakage must not be more than 0.5 cc/minute.").
- Non-STE: "Set the TEST switch to the middle position and release the SHORT-CIRCUIT TEST switch." → STE: "A. Set the TEST switch to the middle position." / "B. Release the SHORT-CIRCUIT TEST switch." (the actions do not occur at the same time)

### Rule 5.3 - Write instructions in the imperative (command) form.
Other sentence structures leave the reader unsure whether the step is required, already done, or someone else's job. Do not use "must" before the imperative unless the instruction is very important for safety or gives an important condition (e.g. "WARNING: IF YOU MUST CUT THE WIRE, ALWAYS USE A PROTECTIVE MASK...").
- Non-STE: "The test can be continued." → STE: "Continue the test."

### Rule 5.4 - When there is a condition that the reader must know about first, start the instruction with a descriptive statement. Then, divide that descriptive statement from the command with a comma.
The comma position can change the meaning: "If the CSD does not operate correctly, disconnect it from the gearbox." vs "If the CSD does not operate, correctly disconnect it from the gearbox."
- Do not write: "Set the switch to NORMAL when the light comes on." → WRITE: "When the light comes on, set the switch to NORMAL."

### Rule 5.5 - Write notes only to give information, not instructions.
Notes contain descriptive text only (they obey descriptive-writing rules); maximum 25 words per sentence. Never use the imperative in a note; never put instructions, requirements, limits, tolerances, or results in a note. Safety-relevant information must be a WARNING/CAUTION, not a note; limits go directly after the related action in the work step. Test: the reader must be able to do the procedure correctly with all notes removed.
- Non-STE: "NOTE: Make sure that the avionics ventilation system continues to operate correctly." → STE: "(6) Make sure that the avionics ventilation system continues to operate correctly." (it is an instruction, so it becomes work step 6)

---

## Section 6 - Descriptive writing

Descriptive writing gives information, not instructions — the imperative form is not permitted. It covers descriptions of items/systems, general-information texts, and notes in procedures.

### Rule 6.1 - Give information gradually.
Give information gradually and make sure that each sentence contains only one subject. Too much information too quickly forces the reader to re-read.
- Non-STE (opens mid-detail): "During the approach to the runway, deviation pointers in the course indicators give commands to fly up or down and left or right..." → STE (topic first, then detail): "The Instrument Landing System (the system) on the aircraft shows data that helps the pilot during the approach to the runway. This system shows the pilot the deviations from the localizer course and the glideslope path. ..."

### Rule 6.2 - Use key words and key phrases to give your text a logical structure.
Key words/phrases connect ideas and show how information is related; connecting words ("and," "but," "then," "thus") and connecting phrases ("as a result," "at the same time") work like traffic signs for the reader. Once you choose key words/phrases, do NOT change them later in the text.
- STE worked example: sentence 2 "This system shows the pilot the deviations from the localizer course and the glideslope path." reuses the key words "system," "show," "pilot" from sentence 1; sentences 3-4 reuse "localizer course" and "glideslope path" and add new information.

### Rule 6.3 - Write short sentences. Use a maximum of 25 words in each sentence.
The descriptive limit is 25 words (vs 20 for procedures) because descriptive text is more complex than procedural text.
- Non-STE: "A smartphone is a cellular telephone that has an integrated computer and many other functions, such as an operating system, internet browsing as well as the ability to run software applications." (31 words) → STE: "A smartphone is a cellular telephone that has an integrated computer and many other functions." (15 words) "It includes an operating system and an internet browser, and it can also operate software applications." (16 words)

### Rule 6.4 - Use paragraphs to show related information.
Paragraphs keep related information together and give the text a logical sequence. Each paragraph starts with a "topic sentence" that tells the reader the topic; the following sentences explain it or add related information.
- STE example: the "Lightning Strike" description is divided into three short paragraphs — (1) where damage occurs (attachment points, listed vertically), (2) how the strike travels and what it damages, (3) the required inspection before the next flight.

### Rule 6.5 - Make sure that each paragraph has only one topic.
The topic sentence is the first and most important sentence; it usually contains a key word and/or a connecting word/phrase to link new information to previous information. Reading only the topic sentences should give a good outline of the text.
- STE example: the Instrument Landing System text has two paragraphs = two topics: paragraph 1 "data to help the pilot" (sentences 1-5), paragraph 2 "how this data is transmitted" (sentences 6-7).

### Rule 6.6 - Make sure that no paragraph has more than six sentences.
If a paragraph has more than six sentences, divide it into two smaller paragraphs. Do not put different topics in the same paragraph.
- STE example: the fuel-manifold description runs six paragraphs of 1, 2, 5, 4, 4, and 2 sentences — all within the six-sentence limit, each on one part of the manifold.

---

## Section 7 - Safety instructions

Definitions (per aerospace/defence technical-publication specifications): a **warning** = risk of injury or death; a **caution** = risk of damage to objects. Other industries may use other words ("danger," "attention," "notice") or symbols — the content must still obey rules 7.1-7.3 (see ISO 45001:2018, ANSI Z535, ISO 3864).

### Rule 7.1 - Use an applicable word (for example, "warning" or "caution") to identify the level of risk.
Do an accurate risk analysis, then: risk of injury or death → "warning"; risk of damage to machines, tools, or equipment → "caution"; both levels of risk together → "warning." Name concrete consequences, not abstract statements.
- Non-STE: "CAUTION: EXTREME CLEANLINESS OF OXYGEN TUBES IS IMPERATIVE." → STE: "WARNING: MAKE SURE THAT THE OXYGEN TUBES ARE FULLY CLEAN. OXYGEN AND GREASE MAKE AN EXPLOSIVE MIXTURE. AN EXPLOSION CAN CAUSE INJURY OR DEATH." (the real risk is injury/death, so caution becomes warning)

### Rule 7.2 - Start a safety instruction with a clear and accurate command or condition.
Begin with the command (what to do / not do). If the reader must know a condition first, lead with the condition clause.
- Command-first STE: "WARNING: DO NOT SWALLOW THE SOLVENT. ..." / Condition-first STE: "WARNING: WHILE YOU USE THE SPRAY PAINT, POINT THE SPRAY AWAY FROM YOUR FACE. THE SPRAY PAINT CAN CAUSE INJURY TO YOUR EYES."

### Rule 7.3 - Give an explanation to show the risk or possible result.
If possible, always tell the reader what can occur if the safety instruction is not obeyed; a clear, specified risk makes the reader more careful. The explanation is the trailing clause of the safety instruction.
- STE: "CAUTION: WHEN YOU ASSEMBLE THE UNIT, DO NOT LET THE PARTS FALL. IF THEY FALL, PERMANENT DAMAGE TO THE PARTS CAN OCCUR." (the second sentence shows the possible result)

---

## Section 8 - Punctuation and word count

STE permits standard English punctuation except the semicolon, defines five hyphen uses and seven parenthesis uses, and gives the counting rules that support the 20/25-word sentence limits.

### Rule 8.1 - You can use all standard English punctuation marks but not the semicolon (;).
The semicolon lets you write very long sentences and is hard to use correctly. Always write two different sentences instead.
- Non-STE: "(1) Examine the removed parts; replace the damaged ones." → STE: "(1) Examine the removed parts for damage. (2) Replace the damaged part(s)."

### Rule 8.2 - Use hyphens (-) to connect words that are directly related.
Five categories: (1) multi-word adjectives before a noun — low-altitude flight, quick-release fastener, up-to-date information; (2) two-word fractions or numbers — forty-seven, three-sixteenths; (3) uppercase letter or number + noun (shape/configuration) — L-shaped bracket, O-ring, 3-prong connector; (4) verbs whose first part is a noun or another part of speech — die-cast, heat-treat, short-circuit; (5) prefix ending in a vowel + root starting with a vowel — pre-amplifier, de-icing, anti-icing. (A hyphen is not a dash: a dash divides ideas, shows a range, or signals a pause.)
- STE: "Use a stiff-bristled brush to remove the corrosion." (multi-word adjective hyphenated before the noun)

### Rule 8.3 - You can use parentheses: to make references to illustrations or text; to include letters or numbers that identify items on an illustration or in a text; to identify the work steps in a procedure; to include abbreviations; to give the singular and plural forms of a noun at the same time; to explain words or a part of a sentence; to include an alternative.
- STE examples per use: "Remove the valve (10, Figure 1)." (reference); "Disconnect the hoses (2) and (12) from the suction ejector (8)." (item identifiers); "(1) Install the locking cap (4) on the body (8)." (work steps); "A Liquid Crystal Display (LCD) is a flat-panel display..." (abbreviation); "Do the applicable test(s)." (singular+plural); "Increase the pressure slowly (not more than 10 psi each minute)." (explanation); "Open the left (right) access panel L42 (R42)." (alternative)

### Rule 8.4 - In a vertical list, a colon (:) has the same effect on word count as a period and shows the end of a sentence.
Before the colon you can use a maximum of 20 words in procedural sentences and a maximum of 25 words in descriptive sentences. Each item after the colon counts as a new sentence with the same limits: 20 words for procedural, 25 words for descriptive.
- STE: "To extinguish a possible fire, portable fire extinguishers are installed in these areas:" (13 words) "- The cockpit" (2 words) "- The cabin" (2 words) "- The cabin sub-compartment" (3 words) "- The crew rest compartment." (4 words)

### Rule 8.5 - When you put text in parentheses, it counts as one word in that sentence.
The words between parentheses also make a new sentence of their own — count them separately in that sentence. Identifiers and abbreviations in parentheses also count as one word.
- STE: "Make sure that the EMER pushbutton switch is released (the EMER legend is off)." — 10 words; the parenthetical text is a separate 5-word sentence.

### Rule 8.6 - Count each of these elements as one word: numbers; numbers together with units of measurement; abbreviations; alphanumeric identifiers; quoted text; titles, headings, and text on placards and labels; proper nouns of individuals, groups, organizations, and geopolitical entities.
1. Numbers: "The spar box has twenty-one ribs." — 6 words. (Do not count numbers that identify paragraphs or work steps — they belong to the document numbering system.)
2. Numbers together with units of measurement: "The unit weighs 20 kg." — 4 words; "The resistance must be 10 Ω" — 5 words.
3. Abbreviations (also acronyms and initialisms): "During this safety check, obey NASA protocols." — 7 words.
4. Alphanumeric identifiers: "Tag circuit breaker 36L7." — 4 words.
5. Quoted text (quotation marks, uppercase, or font differences): "Touch the "Service Overview" arrow to select the function page." — 9 words; a formula such as "C = (A - B) - 0.063 mm" is quoted text = 1 word.
6. Titles, headings, and text on placards and labels (word groups you cannot change): "Before you start a repair, refer to the Structural Repair Manual for the applicable safety procedures and precautions." — 16 words; a full placard or label text ("FRAGILE - Please handle with care.") = 1 word.
7. Proper nouns of individuals, groups, organizations, and geopolitical entities: "The first president of the United States of America was George Washington." — 8 words.

### Rule 8.7 - Hyphenated words count as one word.
Groups of words that function as an adjective before a noun are hyphenated and count as one word; a hyphenated group in a long technical noun also counts as one word.
- STE: "Clean the surface with a soap-and-water solution." — 7 words; "Main-gear-door retraction-winch handle" — 3 words.

---

## Section 9 - Writing practices

How to rewrite when word-for-word replacement fails, how to use approved words correctly, and how to keep a consistent style — plus eight advisory General recommendations (not STE rules).

### Rule 9.1 - Use a different sentence construction to write a sentence when a word-for-word replacement is not sufficient.
A word-for-word replacement works only when the approved alternative has the same part of speech AND does not change the meaning. A different construction is necessary when: (1) the grammatical structure must change to use the alternative; (2) the replacement gives a meaningless result; (3) the approved alternative changes the meaning; (4) the word is not in the dictionary at all. Ask: "What is the meaning of the word in this context?" and "What is the action a reader must do?" The primary objective of STE is that readers immediately understand each sentence that they read.
- Non-STE: "The oil level on the sight gauge must be visible during the test." → STE: "During the test, make sure that you can see the oil level on the sight gauge." ("Visible" is replaced by the verb "see," so the construction changes.)

### Rule 9.2 - Use each approved word correctly.
Read the approved-meaning column before using a word: approved words usually have only one approved meaning and one approved part of speech. A small set of frequent words is approved as more than one part of speech with more than one meaning (e.g. "flush" verb/adjective).
- Non-STE: "Wear protective clothing." → STE: "Use (or put on) protective clothing." ("Wear" is approved only as a verb meaning "to become damaged by friction.")

### Rule 9.3 - When you use two words together, do not make phrasal verbs.
Approved words must keep their dictionary meanings; combining them into a phrasal verb creates a new, unapproved meaning. Phrasal verbs are usually not listed as "not approved" in the dictionary, so check yourself. Only a few phrasal verbs (e.g. "put on," "come on") are approved, each with a restricted meaning.
- Non-STE: "After you put out the fire, close the valve on the fire extinguisher." → STE: "After you extinguish the fire, close the valve on the fire extinguisher."

### Rule 9.4 - When you select terminology or wording, always use a consistent style.
Use the same terminology and the same wording each time the same type of work step occurs; the reader recognizes it and understands faster. Two STE-correct variants of the same instruction ("Lubricate the two bolts with a small quantity of oil." vs "Apply a small quantity of oil to the threads of the two bolts.") must not alternate — select one and reuse it.
- Non-STE: an 8-step procedure calls item (9) "main body," "body," and "body assembly" and mixes "torque" / "torque-tighten." → STE: always "body assembly (9)"; always "Torque each of the ... bolts to ... Nm."

### General recommendations (GR) — advisory guidance, not STE rules

- **GR-1 - The conjunction "that".** Use "that" to connect a subordinate clause after verbs such as "make sure," "show," "recommend" — as much as possible, to prevent ambiguity and help translation. WRITE: "Make sure that the valve is open."
- **GR-2 - The preposition "with".** "With" has three approved meanings (association/relationship; help or sharing; means or instrument) and can be ambiguous ("Install the panel with the green fasteners."). Re-read every "with" sentence; when replacing it, keep the primary action verb of the work step ("Seal the opening with tool TS9867.", not "Use tool TS9867 to seal the opening.").
- **GR-3 - How to use pronouns.** Use only the pronouns approved in the dictionary (not "she" or "he"). If a pronoun can refer to more than one noun, replace it with the noun it refers to ("...the pins can become damaged.", not "...they can become damaged.").
- **GR-4 - The pronoun "this".** Make sure the reader knows what "this" refers to; if it can refer to more than one item, give the applicable context again ("If the cover is locked, this can cause damage to the probe.").
- **GR-5 - False friends.** A word that looks like one in your native language may mean something different in English (English "disposition" ≠ Italian "disposizione"). Non-native writers must confirm the English meaning.
- **GR-6 - Latin abbreviations.** Do not use Latin abbreviations ("e.g.," "i.e.," "etc."); use English words ("for example," "that is," "and so on") or omit them when unnecessary.
- GR-7 - Inclusive language. Not covered in this skill (excluded on user instruction).
- **GR-8 - Possessive form.** The possessive form (Saxon genitive, apostrophe + "s": "the manufacturer's instructions") is permitted in STE, but use it correctly — if you are not sure the sentence is correct, do not use it; it is not easy for all non-native readers. Refer to applicable specifications and style guides.

---

## Appendix A - Subject-to-rule index

From the front matter (pages SRI-1..SRI-4). A `#` after a section number (for example, `7#`) shows the subject applies to all or most rules in that section.

| Subject | Rule |
|---|---|
| Abbreviations | General introduction, 1.5, 2.2, 8.3, 8.5, 8.6 |
| Acronyms | 8.6 |
| Action | 3.7 |
| Active voice | 3.6 |
| Adjectives (how to use them) | 1.4, 1.7, 1.13, 2#, 3.2, 3.3 |
| Adjectives (part of speech) | Part 2, Introduction |
| Adverb (part of speech) | Part 2, Introduction |
| American English spelling | General introduction, 1.14 |
| Approved meaning | 1.3, 9.2 |
| Approved words | 1.1, 1.2, 9.2 |
| Articles (how to use them) | 4.5 |
| Articles (part of speech) | Part 2, Introduction |
| Authoring tools | General introduction |
| Base form of a verb | 3#, Part 2, Introduction |
| Cautions | 5.1, 7# |
| Change form | General introduction |
| Colons | 4.3, 8.4 |
| Command form of the verb (Imperative form) | 3.2, 3.6, 5.3 |
| Company glossary | 1# |
| Comparative form of adjectives | 1.4 |
| Computer processes and applications | 1.12 |
| Conjunctions (part of speech) | Part 2, Introduction |
| Connecting words and phrases | 4.4, 6.2 |
| Consistent style | 9.4 |
| Controlled natural language | General introduction |
| Dashes | 4.3, 8.2 |
| Demonstrative adjectives | 4.5 |
| Descriptive writing | 3.6, 4.1, 6# |
| Different sentence constructions | 1.2, 9.1 |
| False friends | 9 – GR-5 |
| Forms of adjectives | 1.4, Part 2, Introduction |
| Future tense (simple) | 3.2, Part 2, Introduction |
| Headings | 8.6 |
| Help (light bulb symbol) | Part 1, all sections. Part 2, applicable entries |
| Hyphens | 2.2, 8.2, 8.7 |
| "-ing" form | 3.5 |
| Imperative form (command form) | 3.2, 3.6, 5.3 |
| Infinitive form (base form of the verb) | 3.2, Part 2, Introduction |
| Initialisms | 8.6 |
| Instructions | 5#, 7# |
| Irregular verbs | 3.1, Part 2, Introduction |
| Items (in a vertical list) | 4.3, 8.4 |
| Jargon words | 1.10 |
| Key phrases | 6.2 |
| Key words | 6.2, 6.5 |
| Latin abbreviations | 9 – GR-6 |
| Law and regulations | 1.5, 1.12 |
| Length of paragraphs | 6.6 |
| Length of sentences | 4.1, 4.2, 4.3, 5.1, 6.3, 8.4 thru 8.7 |
| List of approved verbs | Part 2, Introduction |
| List of recurring errors | Part 2, Introduction |
| Logic (descriptive writing) | 6# |
| Manufacturing processes | 1.12 |
| Meaning, one for each word | 1.3 |
| Multi-word nouns | 2# |
| Notes | 5.5 |
| Nouns (part of speech) | Part 2, Introduction |
| Nouns (how to use them) | All sections |
| Noun terms | 1.1 |
| Omission of words | 4.2 |
| Oral communication | General introduction |
| Paragraphs | 6.4, 6.5, 6.6 |
| Parentheses ( ) | 8.3, 8.5 |
| Parts of speech | 1.2, 3.7, 9.1, Part 2, Introduction |
| Passive voice | 3.3, 3.4, 3.6 |
| Past participle form (as an adjective) | 3.3 |
| Placards | 1.5, 8.6 |
| Possessive form (Saxon genitive) | 9 – GR-8 |
| Preposition (part of speech) | Part 2, Introduction |
| Procedural writing (procedures) | 5# |
| Pronouns (how to use them) | 9 – GR-3 |
| Pronouns (part of speech) | Part 2, Introduction |
| Proper nouns | 8.6 |
| Punctuation | 8.1 thru 8.3 |
| Quoted text | 1.5, 8.6 |
| Reference documents | General introduction |
| Regional words | 1.10 |
| Regular verbs | 3.1, Part 2, Introduction |
| Safety instructions | 7# |
| Semicolons | 8.1 |
| Sentences | 4#, 5#, 6# |
| Simple future tense | 3.3 |
| Simple past tense | 3.3 |
| Simple present tense | 3.3 |
| Slang words | 1.10 |
| Spelling | 1.14 |
| Subject fields | 1.1, 1.5, 1.12 |
| Superlative forms of adjectives | 1.4 |
| Technical nouns | 1.1, 1.5 thru 1.13, 2.2 |
| Technical verbs | 1.1, 1.12, 1.13 |
| Technical translation | General introduction |
| Terminology database | 1# |
| Text formatting | General introduction |
| That (how to use) | 9 – GR-1 |
| This (how to use) | 9 – GR-4 |
| Titles | 8.6 |
| Topic (subject of paragraph) | 6.5 |
| Topics, one for each paragraph | 6# |
| Topics, one for each sentence | 4.1 |
| Training (in STE) | General introduction |
| Units of measurement | General introduction, 1.5, 8.6 |
| Verb forms | 1.4, 3.2, Part 2, Introduction |
| Verb terms | 1.1 |
| Verbs | 3#, Part 2, Introduction |
| Vertical lists | 4.3, 8.4 |
| Warnings | 7# |
| With (how to use) | 9 – GR-2 |
| Word count | 8.4 thru 8.7 |
| Word-for-word replacement | 1.2, 9.1 |
| Words | 1#, all sections |
| Words (that are not approved) | 1.1, 1.2, 1.6, 9# |
| Writing practices | 9# |

---

## Appendix B - What changed in Issue 9

- Issue 9 (2025-01-15) fully replaces all previous issues; its primary focus is harmonization of terminology with ISO standards, and the subtitle changed to "Standard for technical documentation."
- The term "technical noun" fully replaces the former term "technical name" in all parts of the document (definitions of technical nouns and technical verbs now appear in Rule 1.1).
- Rule 4.5 (articles and demonstrative adjectives) is new to Section 4 — it was previously Rule 2.3, removed from Section 2 and moved here.
- Rule 1.5 gained Category 21 "Law and regulations" and Category 22 "Animals, plants, and other life forms"; all category titles were revised and short explanatory texts added.
- Rule 1.12 was restructured: Category 3 now includes subcategories for applicable subject fields (it fully replaces the previous category 4), and a new Category 4 (Law and regulations) was created.
- Rule 8.6 sub-item 2 got a revised word count for numbers together with units of measurement, and sub-item 7 added proper nouns of individuals, groups, organizations, and geopolitical entities.
- General recommendations GR-7 and GR-8 (Possessive form) are new; "Help" (light-bulb) guidance was added to many rules.