Controlled Languages

About Controlled Languages

Controlled languages (sometimes called controlled natural languages or CNLs) are subsets of human languages, such as English or Chinese. Controlled languages use restricted grammar rules and vocabularies (typically between 800 and 1,000 words) to reduce or eliminate ambiguity and complexity. They are often used to simplify technical communication, especially for the benefit of non-native readers. They are also used to improve machine translation of source content, which typically results in reduced translation costs.

Traditionally, controlled languages fall into two major categories, simplified controlled languages and logic-based controlled languages.

Simplified Controlled Languages

Simplified controlled languages require that the writer adhere strictly to a very limited vocabulary and to general rules, such as:

  • Write short and grammatically simple sentences
  • Use nouns instead of pronouns
  • Use determiners
  • Use active instead of passive

Examples of common simplified controlled languages include ASD Simplified Technical English, Caterpillar Technical English, Voice of America’s Special English, and IBM’s Easy English. (Newspeak, the fictional language in the novel 1984 by George Orwell, is also an example of a controlled natural language.)

Logic-based Controlled Languages

Logic-based controlled languages provide more formal syntax and semantics than simplified controlled languages. Writers follow specific rules that are enforced by automated software tools. Content can be classified and processed like data.

Advantages to logic-based controlled languages include more accurate machine translation results and better search and query processing across multiple languages. Complex linguistic and statistical analysis of source and target content is also made easier with logic-based controlled languages.

Examples of logic-based controlled languages include Attempto Controlled English, Common Logic Controlled English (CLCE), Uwe Muegge’s Controlled Language Optimized for Uniform Translation (CLOUT), and Processable ENGlish (PENG).

Key Words

Plain English, Plain English Movement (PEM), Plain English Campaign (PEC), plain language, information design, Simplified English (SE), nonnative speakers, American English, idiomatic meaning, Latinate

Other Resources

Annotated Bibliographies

Controlled Languages from Wikipedia

Controlled Language for Multilingual Machine Translation

Controlled Languages – a research note by Namahn


Jeff Huset created this page.