Simplified Technical English (Simplified English)

Characteristics and components

The core of Simplified English is twofold: an approved word list and a set of writing rules. The approved word list limits which words may be used and often gives a single meaning for each approved word. The writing rules guide grammar, sentence structure, and style. Typical recommendations include using the active voice, writing short sentences, choosing specific verbs, avoiding idioms and figurative language, and using the imperative form for procedural steps. Together these controls reduce polysemy (words with multiple meanings) and stylistic variation that can confuse readers or translators.

History and standards

The method was developed in the late 20th century to address clarity problems in aerospace maintenance documentation. An industry association originally created the first controlled vocabulary and rules, and the work has since been maintained and updated by a broader industry body. The current published standard for this controlled language is known as ASD-STE100, which is maintained by the Simplified Technical English Maintenance Group (STEMG) under the AeroSpace and Defence Industries Association of Europe (ASD). The standard is periodically revised to reflect user feedback and evolving needs.

Uses and benefits

Simplified English is used primarily for technical manuals, safety notices, installation guides, and procedures where misunderstanding can have serious consequences. Practical benefits include:

• Improved comprehension for readers whose first language is not English.
• Reduced risk of misinterpretation in safety- or maintenance-critical contexts.
• Faster human reading and easier learning of procedures.
• Simpler and more accurate human translation and better results from computer-assisted translation and machine translation tools (machine translation tools).

Examples and common rules

To illustrate, the controlled vocabulary distinguishes between forms that are spelled the same but have different parts of speech or meanings. One example often cited is the words close and closed. A rule might permit the verb close in an instruction such as "Close the valve," and approve the adjective closed to mean "not open" ("The valve is closed"). If the meaning is "near," the adjective near is specified instead of close to avoid confusion ("Do not go near the valve"). Writers are encouraged to use short, direct sentences and to avoid synonyms that could introduce ambiguity.

Distinctions and notable facts

Simplified Technical English differs from general "plain English" or simplified language used in English teaching because it is intentionally prescriptive and tailored to technical content. It is not a reduction of vocabulary for basic literacy but a standardized approach to eliminate ambiguity in technical writing. Organizations adopt the standard to improve documentation quality, to comply with industry practices, or to make localization and automated processing more reliable. For further discussions of its effectiveness and research on comprehension, see related studies and resources (research).