不是反义词,mature意思是成熟,amateur意思是业余爱好、业余的,例如:
1.Although tom's only an amateur he's a first-class player.虽然汤姆只是个业余爱好者,但却是一流的高手。
2.After he won the amateur championship he turned professional.他获得业余赛冠军后就转为职业运动员了。
3.He has that je ne sais quoi that distinguishes a professional from an amateur.他有那种难以言表的特质,体现出他是专业而非业余的。