sheep的复数形式是：sheep，单复数同形。

词语用法：

1、sheep的意思是“羊,绵羊”,是可数名词,单复数同形。

2、sheep用于比喻可表示人“胆小”。

　　常用短语

　　1、a wolf in sheep's clothing

　　披着羊皮的'狼 sb who appears to be harmless but is in fact dangerous

　　2、black sheep

　　害群之马,败类,不肖之子 sb who does not conform to the family's wishes

　　3、count sheep

　　心里计数以求入睡 keep counting to oneself in an attempt to fall asleep

　　4、separate the sheep from the goats

　　区别好坏〔优劣〕 tell those who are good, able, etc. from those who are not