"buy"的复数形式是 buys。例如：

1. She buys groceries every week.

2. They bought a new house.

"buy"作为动词时，通常使用其第三人称单数形式"buys"。而作为名词时，"buy"是不可数名词，没有复数形式。不过，"buy"的动名词形式"buying"则是可数名词，具有复数形式"buyings"。例如：

1. I enjoy buying books.

2. They are discussing their recent buys.