series/'sɪəriːz $ 'sɪr-/

n. several events or things that happen one after another

n. 〖复同单〗 [C,常S] 系列：[a series of sth + v.单] a series of experiments 一系列实验

◇a series of events 一系列事件

◇A series of problems led to the crisis. 一系列问题引起了这次危机。

巧记 以-s结尾且单复同形的名词还有means。