过去式是用在一般过去时的,；过去分词用在完成时态的，过去分词要和其它成分连用.
1.have has +过去分词 （现在完成时）
2.had+过去分词（过去完成时）
3.be+过去分词（被动语态）
相关介绍
如;
during the 1980s,revoluntionry changes in the work lives of Americans,caused by technological advance which will permit greater productivity by fewer workers,will likely result in shortened work weeks,increased released time for workers,and increased pressure for early retirements.
revoluntionry changes 是主语中心词,caused by.是过去分词修饰主语．（其前没有助动词,这是判断是否是过去分词或过去式的一个重要的标志．所以很容易看出它不作谓语．）
will likely result in 是谓语
shortened work weeks 是宾语1 increased released time 是宾语2 increased pressure 是宾语3 这些~ed分词都是作形容词用．很容易理解．
