a language in which the interpreter is perfectly fluent, but which is not a mother tongue. An interpreter can work into this language from one or several of their other working languages, but may prefer to do so in only one mode of interpretation, either consecutive or simultaneous (often in 'consecutive' because it is not as fast). It is also considered an active language for the interpreter.

the language which the interpreter understands perfectly but into which they do not work. They will interpret from this (these) language(s) into their active languages.

the interpreter's mother tongue (or its strict equivalent) into which they work from all their other working languages in both consecutive and simultaneous interpretation. It is the language they speak best, and in which they can easily express even complicated ideas. It is therefore an active language for the interpreter