Question

为什么当是复数时have要变成has?have不是单数形式吗

Answer 1

have 是单词原形,has是它的第三人称单数形式.

在一般现在时,当主语是第三人称单数时,谓语动词用has.（这种现象在英语中叫做主谓一致）.比如：

She has a book.

I have a book.

They have a lot of books.