A-language
In order to describe the languages required at an international conference or, in the case of interpreters, to be able to make a statement about the degree of mastery of the respective languages, one makes use of certain terms which will be explained here in the following.
About the terms active and passive Language:
An active language means that interpreters can both understand and speak that language well. A passive language, on the other hand, interpreters can only understand well, but they will not interpret into that language.
An active language at a conference states that this language is spoken by the speaker, by panelists or in the room during discussion contributions, a passive language, on the other hand, is not used at all in the conference room (e.g. when guests of a language only appear as listeners, requests to speak in this language are not scheduled/allowed).
On the terms A-language, B-language and C-language:
The A-language of an interpreter is his mother tongue. If he has grown up multilingual, he may even have several mother tongues in exceptional cases. Interpreting into this language is best after many years of professional experience. The A language is an "active" language.
The B language is a language in which an interpreter is almost as proficient as in his or her native language. Accordingly, he can both understand and speak it perfectly. This is also an "active" language.
Finally, the C-language: The interpreter here is able to understand this language very well and to reproduce it in other languages, but he does not interpret into this language. This is therefore a "passive" language.