A first language (also mother tongue, native language, arterial language, or L1) is the language a person first learns. A person's first language helps them understand words and concepts in the style of that first language.
"First language" sometimes does not mean this, however.
Sometimes first language means the language a person speaks best (his second language is language he speaks less well than his first language, etc.).
Sometimes first language, second language and third language show how well one speaks a language, so a person can have more than one first language or second language.
- Bloomfield, Leonard. Language ISBN 81-208-1196-8
- Alan Davies. The native speaker: myth and reality. ISBN 1-85359-622-1