1.语法形式上的一致。
主语为单数形式,谓语动词用单数形式;主语为复数形式,谓语动词也用复数形式。例如:
The number of the mistakes was surprising.
Jane and Mary look healthy and strong.
2.意义上一致。
1)主语形式虽为单数,但意义为复数,谓语动词用复数。例如:
The crowd were running for their lives.
单数形式表示复数意义的词有people,police,cattle,crowd等。
2)主语形式为复数而意义上却是单数,谓语动词用单数。例如:
The news is inspiring.
形复意单的单词有news,works(工厂)和一些以ics结尾的学科名称,如physics,politics,mathematics等。
3.就近原则。
即谓语动词的单、复数形式取决于最靠近它的词语。如用连词or,either...or,neither...nor,not only...but also等连接的并列主语,如果一个是单数,一个是复数,谓语动词与靠近它的主语一致。例如:
Either your students or Mr Wang knows this.
Not only the teacher but also his students like playing football.
