Tomodachi (友達) means "friend." It's a common and casual word used to refer to someone you know well and share a friendly relationship with. You can use it for both male and female friends, and for a single friend or a group of friends. Example: 彼女は私の友達です。(Kanojo wa watashi no tomodachi desu.) = She is my friend.

親(した)しい関(かん)係(けい)の人(ひと)物(ぶつ)を指(さ)す一(いっ)般(ぱん)的(てき)な言(こと)葉(ば)です。例(れい)：彼(かの)女(じょ)は私(わたし)の友(とも)達(だち)です。