---
title: "Simplified Technical English: overview"
subtitle: ASD-STE100, a controlled language for aircraft maintenance documents
cols: 8
specification: ASD-STE100
source: asd-ste100.org
---

## A Document structure {span=2 meta="ASD-STE100 specification"}
```tree
ASD-STE100 | Simplified Technical English
  Part 1: Writing rules
    `Section 1` Words
    `Section 2` Noun clusters
    `Section 3` Verbs
    `Section 4` Sentences
    `Section 5` Procedures
    `Section 6` Descriptive writing
    `Section 7` Safety instructions
    `Section 8` Punctuation and word counts
    `Section 9` Writing practices
  Part 2: Dictionary
    Approved words | Keyword in UPPERCASE, one meaning
    Unapproved words | lowercase, with approved alternative
    Technical names | company terms, defined categories
    Technical verbs | company verbs, defined categories
```
About 900 approved words. Each word has one part of speech and one meaning.

## B Anatomy of STE sentences {span=4 meta="annotated examples"}
```annot
# Original text, not STE | unapproved words in red
It is [imperative]{!} that the operator [ensures]{!} the hydraulic reservoir is [replenished]{!} [prior to]{!} [commencing]{!} operation.
# 1 Procedural sentence | 13 words, limit 20
[Make sure]{Approved verb, command form} that [the hydraulic reservoir]{Technical name, max 3 words} is [full]{Not "replenished"} [before]{Not "prior to"} [you]{Active voice} [start]{Not "commencing"} the operation.
# 2 Safety instruction
[WARNING:]{!WARNING = risk of injury} [Do not touch the brake unit until it is cool.]{First: a clear, simple command} [Hot parts can cause injury.]{Then: the risk}
# 3 Descriptive sentence | 12 words, limit 25
The pump [supplies]{Simple present tense} fuel to the engine when the switch is on.
> Max 6 sentences per paragraph. One topic per paragraph.
```

## C Verb forms {span=2 meta="Section 3"}
| Form | Example | Status |
|---|---|---|
| Command (imperative) | `Close the valve.` | ok Approved |
| Simple present | `The valve closes.` | ok Approved |
| Simple past | `The valve closed.` | ok Approved |
| Simple future | `The valve will close.` | ok Approved |
| Infinitive | `Turn the knob to close it.` | ok Approved |
| Past participle (as adjective) | `The closed valve` | ok Approved |
| Progressive (-ing) | `The valve is closing.` | no Not approved |
| Perfect | `The valve has closed.` | no Not approved |
| Passive, in procedures | `The valve must be closed.` | no Not approved |

Use the -ing form only inside a technical name, for example "landing gear".

## D Dictionary entries {span=4 rows=2 meta="Part 2 format"}
| Word (part of speech) | Status | Meaning or alternative | Approved example | Not approved |
|---|---|---|---|---|
| `CLOSE (v)` | ok Approved | To move together; to stop flow | CLOSE the valve. | – |
| `close (adj)` | no Not approved | NEAR | Put the tool NEAR the panel. | ~~Put the tool close to the panel.~~ |
| `commence (v)` | no Not approved | START | START the pump. | ~~Commence pumping.~~ |
| `ensure (v)` | no Not approved | MAKE SURE | MAKE SURE THAT the switch is off. | ~~Ensure the switch is off.~~ |
| `prior to (prep)` | no Not approved | BEFORE | BEFORE you start the engine, | ~~Prior to starting the engine,~~ |
| `replenish (v)` | no Not approved | FILL | FILL the reservoir. | ~~Replenish the reservoir.~~ |
| `utilize (v)` | no Not approved | USE | USE a torque wrench. | ~~Utilize a torque wrench.~~ |
| `approximately (adv)` | no Not approved | ABOUT | Wait for ABOUT 10 minutes. | ~~Wait approximately 10 minutes.~~ |
| `TEST (v)` | ok Approved | To find if it operates correctly | TEST the circuit. | – |
| `in order to` | no Not approved | TO | Remove the panel TO get access. | ~~Remove the panel in order to access.~~ |

Approved words are in UPPERCASE. Unapproved words are in lowercase. An approved word keeps only its listed meaning and part of speech.

## E Writing rule limits {span=2 rows=2 meta="maximum values"}
```limits
Procedural sentence | max 20 | words
Descriptive sentence | max 25 | words
Descriptive paragraph | max 6 | sentences
Noun cluster | max 3 | words
Instructions in each sentence | max 1 | | except simultaneous actions
```
- Use the same word for the same thing every time.
- Do not leave out words like "the", "a" and "this".
- Use the active voice in procedures.
- Use vertical lists for complex text.
- Write one topic in each paragraph.

## F History {span=2}
```timeline
1979 | AECMA starts work | on controlled English for airlines
1986 | First guide | AECMA Simplified English Guide
2005 | ASD-STE100 | after AECMA joins ASD in 2004
*Now | Free download | revised by the ASD STEMG
```
STEMG: Simplified Technical English Maintenance Group.

## G Title block {span=2 bare}
```kv
* Title: Simplified Technical English: overview
Specification: ASD-STE100
Owner: ASD
Original domain: Aircraft maintenance
Now also used in: Defence, rail, industry
Source: asd-ste100.org
Sheet: 1 of 1
```