pass（通过）是（及物和不及物）动词，passed是过去式，也是过去分词；past（过去，过去的，超过，超出，越过， 经过）是形容词、名词、介词、副词。如;

He passed the exam. The Bill(议案） has been passed.

He passed through the doorway into Room 203.

I knew from past experience that alternative therapies could help. 根据过去的经验，我知道替代疗法可能有用。

It's ten past eleven. 现在是11点过10分。

In the past, about a third of the babies born to women with diabetes were lost. 过去，患有糖尿病的女性生下的孩子中约有1/3夭折了。

But the years went past, and the doctor became old. 但几年过去了，医生也老了。