spectator [spekˈteɪtər]

Spectators literally means “people who watch”.It is used more commonly to mean a person who watches at a show, game, or other event, especially a sports event.

"spectator"字面上的意思是“观看的人”。它更常用于指观看表演、比赛或其他活动，特别是体育活动的人。

• The stadium holds 75 000 spectators.该体育场可容纳7.5万名观众。
• There were thousands of spectators at the game.比赛有成千上万的观众。
• Tennis ranks second after football as the most popular spectator and participation sport. 网球仅次于足球是排行第二最受观众欢迎和参与的体育项目。

spectator

audience [ˈɔːdiəns]

a group of people who have gathered to watch or listen to sth such as a play or concert.

"audience "指聚集在一起观看或听某物如戏剧或音乐会的一群人。（集体名词）

Audience is broader and can be used when talking about people at a concert, a play, a talk, people watching a film or TV show or even people reading a book.

"audience "应用范围更广，可以指在音乐会、话剧、谈话、看电影或电视节目的人，甚至是在读书的人。

• The audience clapped when she finished speaking.她讲完后观众鼓掌。
• The audience at once greeted him warmly. 观众立即对他作出了热情的反应。
• Television has transformed the size and social composition of the audience at great sporting occasions. 电视改变了重大体育赛事观众的规模和其社会阶层构成结构

audience

总结：从他们的释义来看，spectator可以指单个的观众。而audience一般是一个集体名词。另外他们的应用范围和场合也不太一样，audience还可以做听众理解，而spectator还可以指旁观者的意思。