was 是am is 过去式 ；were 是are 过去式 .
具体用法如下：
1.was用于 I ,he ,she,it 以及 单个人作主语的句子.
例如：
I was born in 1998.
He was a doctor three years ago.
She was at home yesterday.
It was Monday yesterday.
Mike wasn't at home this morning.
2.were用于you,they,we 以及两个以上的人作主语的句子.
例如：
You were at home yesterday.
They were at the playground an hour ago.
We were singing in the room an hour ago.
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