In the field of translation

Translation

Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. Whereas interpreting undoubtedly antedates writing, translation began only after the appearance of written literature; there exist partial translations of the Sumerian Epic of...

, a translation unit is a segment of a text which the translator treats as a single cognitive unit for the purposes of establishing an equivalence. The translation unit may be a single word, a phrase, one or more sentences, or even a larger unit.

When a translator segments a text into translation units, the larger these units are, the better chance there is of obtaining an idiomatic translation. This is true not only of human translation, but also in cases where human translators use computer-assisted translation

Computer-assisted translation

Computer-assisted translation, computer-aided translation, or CAT is a form of translation wherein a human translator translates texts using computer software designed to support and facilitate the translation process....

, such as translation memories

Translation memory

A translation memory, or TM, is a database that stores so-called "segments", which can be sentences or sentence-like units that have previously been translated. A translation memory system stores the words, phrases and paragraphs that have already been translated, in order to aid human translators...

, and also when translations are performed by machine translation

Machine translation

Machine translation, sometimes referred to by the abbreviation MT is a sub-field of computational linguistics that investigates the use of computer software to translate text or speech from one natural language to another.On a basic...

systems.