Translation is the interpretation of the meaning of a text in one language (the "source text") and the production, in another language, of an equivalent text (the "target text," or "translation") that communicates the same message. Translation must take into account a number of constraints, including context, the rules of grammar of the two languages, their writing conventions, their idioms and the like. Consequently, as has been recognised at least since the time of the translator Martin Luther, one translates best into the language that one knows best. Traditionally translation has been a human activity, though attempts have been made to computerise or otherwise automate the translation of natural- language texts (machine translation) or to use computers as an aid to translation (computer- assisted translation).