First language and Tongue

First language noun - One's native language; the language learned by children and passed from one generation to the next.

Tongue and first language are semantically related. In some cases you can use "Tongue" instead a noun phrase "First language".

Tongue noun - The stock of words, pronunciation, and grammar used by a people as their basic means of communication.

First language and tongue are semantically related. Sometimes you can replace phrase "First language" with "Tongue", this terms are similar.