在学习英语词汇中，有时同义词的辨析是很不容易的，我们一般从三方面进行区分，即：语法、语义和文体。语法主要是词性、搭配、句式等的区分;语义主要是词义的本义、引申义、比喻义和内涵和外延等的区分;文体主要是正式和非正式、褒义和贬义等的区分。

　　时代

　　period: It indicates any passage of time, great or small.

　　epoch: It indicates a long period of time marked by events or development of a particular kind.

　　The first flight into space marked a new epoch in the history of mankind.

　　era: It refers to a very long period of time marked by a particular feature in a great new era of world revolution

　　age: It shows a particular