L1 is the abbreviation for "Language 1". Other terms used include first language, mother tongue, native language, or arterial language.
 Use in the classroom
On the one hand, given that the classroom is an artificial environment and that time is very often of the essence, a quick translation of a certain word or expression into the students’ mother tongue can save very valuable and limited class time which can be dedicated to other, possibly more essential elements of language learning.
As idiomatic expressions are usually impossible for a non-native speaker to understand from a context and cannot be translated literally, teachers should be able to facilitate the students’ comprehension by providing an equivalent expression in their own language.
On the other hand, precisely because of limited class time, students should be “trained” and encouraged to develop the four underlying components of language set out by Canale and Swain (1980) to define linguistic competence, especially that of strategic competence, in order for them to get used to solving their own “problems” by themselves, without depending too much on the teacher.
In other words they should:
- Practice using context to enable them to guess meaning.
- Not be afraid of making mistakes.
There is obviously a specific use for L1 in classes concentrating on translation work, including, but not limited to, ESP courses and the like.
 See also
- Correcting mistakes
- Debate:Use of L1 in the classroom
- Non-verbal communication
- Translation in class