630　spectator，audience，observer，looker-on和witness

① spectator指观看不需要注意听的展览、表演或娱乐活动等的观众，如看体育比赛等。

Many spectators stood around the football field to watch the game. 许多观众围着足球场看比赛。

② audience指参加音乐会、演讲或观看戏剧等的观众、听众。

The audience was enjoying every minute of the show. 观众自始至终欣赏这次演出。

③ observer指对事物、细节认真观察的人，如科学工作者、军事或外交观察员等。

He was a skilled observer of insects. 他擅长观察昆虫。

④ looker-on/onlooker指抱有随便的、不介入态度的旁观者。

There was a great crowd of lookers-on at the fire. 着火的地方有一大群人旁观。

⑤ witness指对某事件有第一手资料因而可以提供证据的人，证人。

A witness was summoned to appear in court. 一位证人被传唤出庭。