词性不同、具体含义不同、用法不同。seat意为“使就坐”、“使坐下”、“能坐下(容纳下)”等，是及物动词。sit表示“坐”、“就坐”，通常是不及物动词。sit的过去分词是sat，但用作表语、定语、宾语补足语等时，却通常要用seated。

sit的例句

The students sit in a circle on the floor.

学生们围坐在地板上。

Come and sit here beside me.

过来坐在我旁边。

Can I sit next to you?

我能坐在你旁边吗？

He took off his coat and sat down.

他脱下外套坐下。

seat的例句

She seated herself at her desk.

她在桌子旁坐下。

He seated himself behind the desk.

他坐在桌子后面。

He seated himself on the sofa.

他坐在了沙发上。

John was seated on my left.

约翰坐在我的左边。