钮

例句：

1. 1. She carefully put the button on her coat.
   她小心翼翼地把纽扣放在她的外套上。
2. 2. The old man used to wear a button as a necklace.
   这位老人过去常戴着一个纽扣当项链。
3. 3. The buttons on his shirt are all undone.
   他的衬衫上的纽扣都解开了。