IV. 用作单数的复数形式主语：
1．如主语是指：time, money, weight, volume, etc. 虽为复数形式，但谓语用单数形式。
Two years is a short time.
One hundred dollars is needed by me.
2．下列单词如：physics，economics，mathematics，statistics，etc；measles，mumps，herpes，etc，news，ethics，politics，etc. 为复数形式，但谓语动词用单数。
Statistics is a dull subject.
Politics is important.
3．书、报、杂志、电影的名称作主语，谓动用作单数。
The New York Times is a good newspaper.
V．下列名词在形式上保持不变，但谓语动词的数取决于其意义：
1．family，team，class，committee，group，audience，faculty，etc.
The family is big.（总体）
His family like to watch TV.（家庭所有成员）
2．species，series，etc.
The species is rare.
These species are common.
3．sheep，deer，etc.
The sheep are eating grass.
The sheep is big.
VI. Chinese, English, French, etc 指语言时，谓动是单数，如与 "the" 搭配，指人民时，谓语动词用复数。
English is used widely.
The English love peace.
VII. 注意下列外来语的单复数形：
单数 复数
basis bases
crisis crises
criterion criteria
phenomenon phenomena
radius radii
alumnus alumni
datum data
medium media
index indices
appendix appendices
alga algae
vita vitae
