noun
casual speech; friendly language
Refers to the informal, casual way of speaking used among close friends, often characterized by plain forms, slang, and dropped particles.
親しい友達同士では、友達言葉で話すのが普通だ。
It's normal to speak in casual speech among close friends.
目上の人に友達言葉を使うのは失礼にあたる。
Using casual speech with a superior is considered rude.
Compound of 友達 (friend) and 言葉 (language, speech).