动词才有过去式和过去分词之分。所谓的动词过去式，它在句子中当谓语，如：He wrote a letter yesterday.wrote是write的过去式，当谓语。而动词的过去分词，它在句子中视情况而定，可以单独或与其它助动词一起当相应的句子成份。如：He has written a letter.written是过去分词，与has一起构成完成时，当谓语。The letter was written by him.written也是过去分词，与was一起构成被动语态，当谓语。He had a letter written this morning.他今天早上叫人写了一封信。written 也是过去分词，在句子中当letter的补语，补充说明信是叫别人写的。This is a book written by a famous writer. written也是过去分词，在句子中当定语，相当于一个定语从句：a book which was written by a famous writer.除此之外，过去分词还可以在某些结构中充当其它的句子成份。比如：with结构，独立主格结构等。
