1. 羽毛
    A bird's feathers are the soft covering on its body. Each feather consists of a lot of smooth hairs on each side of a thin stiff centre.

    e.g. ...a hat that she had made herself from black ostrich feathers.
           她用黑色鸵鸟羽毛给自己做的帽子
    e.g. ...a feather bed.
           羽毛褥垫床

2. 同类的人;志趣相投的人;一丘之貉
    If you describe two people as birds of a feather, you mean that they have very similar characteristics, interests, or beliefs.

    e.g. She and my mother were birds of a feather.
           她和我妈妈是一个类型的人。

3. 可引以为豪的事;荣耀的事;有好处的事
    If you describe something that someone has achieved as a feather in their cap, you mean that they can be proud of it or that it might bring them some advantage.

    e.g. Harry's appointment to this important post was a feather in his cap.
           哈里被任命担任如此要职，这是件荣耀的事。

4. to feather one's nest -> see nest
    to ruffle someone's feathers -> see ruffle