在英語句子里，謂語受主語支配，其動詞必須和主語在人稱和數(shù)上保持一致，這就叫主謂一致。尋其規(guī)律，大致可歸納為三個原則，即語法一致、邏輯意義一致和就近一致原則。
（一）語法一致原則：語法上一致就是謂語動詞和主語在單、復數(shù)形式上保持一致。
1、以單數(shù)名詞或代詞、動詞不定式短語、動名詞短語或從句作主語時，謂語動詞一般用單數(shù)形式；主語為復數(shù)時，謂語動詞用復數(shù)形式。如：His father is working on the farm. / To study English well is not easy. / What he said is very important for us all. / The children were in the classroom two hours ago. / Reading in the sun is bad for your eyes.
注意：由what引導的主語從句，后面的謂語動詞多數(shù)情況用單數(shù)形式，但若表語是復數(shù)或what從句是一個帶有復數(shù)意義的并列結構時，主句的謂語動詞用復數(shù)形式。如：What I bought were three English books. / What I say and do is (are) helpful to you.
2、由連接詞and或both … and連接起來的合成主語后面，要用復數(shù)形式的謂語動詞。如：Lucy and Lily are twins. / She and I are classmates. / The boy and the girl were surprised when they heard the news. / Both she and he are Young Pioneers.
注意：① 若and所連接的兩個詞是指同一個人或物時，它后面的謂語動詞就應用單數(shù)形式。如：The writer and artist has come.; / ② 由and連接的并列單數(shù)主語前如果分別有no, each, every more than a (an) , many a (an)修飾時，其謂語動詞要用單數(shù)形式。如：Every student and every teacher was in the room.. / No boy and no girl likes it.
3、主語為單數(shù)名詞或代詞，盡管后面跟有with, together with, except, but, like, as well as, rather than, more than, no less than, besides, including等引起的短語，謂語動詞仍用單數(shù)形式；若主語為復數(shù)，謂語用復數(shù)形式。如：Mr Green, together with his wife and children, has come to China. / Nobody but Jim and Mike was on the playground. / She, like you and Tom, is very tall.
4、either, neither, each, every 或no +單數(shù)名詞和由some, any, no, every構成的復合不定代詞，都作單數(shù)看待。如：Each of us has a new book. / Everything around us is matter.
注意：① 在口語中當either或neither后跟有“of+復數(shù)名詞（或代詞）”作主語時，其謂語動詞也可用復數(shù)。如：Neither of the texts is (are) interesting. ② 若none of后面的名詞是不可數(shù)名詞，它的謂語動詞就要用單數(shù)；若它后面的名詞是復數(shù)，它的謂語動詞用單數(shù)或復數(shù)都可以。如：None of us has (have) been to America.
5、在定語從句時，關系代詞that, who, which等作主語時，其謂語動詞的數(shù)應與句中先行詞的數(shù)一致。如：He is one of my friends who are working hard. / He is the only one of my friends who is working hard.
6、如果集體名詞指的是整個集體，它的謂語動詞用單數(shù)；如果它指集體的成員，其謂語動詞就用復數(shù)形式。這些詞有family, class, crowd, committee, population, audience等。如：Class Four is on the third floor. / Class Four are unable to agree upon a monitor.
注意：people, police, cattle等名詞一般都用作復數(shù)。如：The police are looking for the lost child.
7、由“a lot of, lots of, plenty of, the rest of, the majority of + 名詞”構成的短語以及由“分數(shù)或百分數(shù)+名詞”構成的短語作主語，其謂語動詞的數(shù)要根據(jù)短語中后面名詞的數(shù)而定。如：There are a lot of people in the classroom. / The rest of the lecture is wonderful. / 50% of the students in our class are girls.
注意： a number of“許多”，作定語修飾復數(shù)名詞，謂語用復數(shù)；the number of“…的數(shù)量”，主語是number，謂語用單數(shù)。
8、在倒裝句中，謂語動詞的數(shù)應與其后的主語一致。如：There comes the bus./ On the wall are many pictures. / Such is the result. / Such are the facts.
（二）邏輯意義一致原則：邏輯意義一致就是謂語動詞的數(shù)必須和主語的意義一致（因有時主語形式為單數(shù)，但意義為復數(shù)；有時形式為復數(shù)，但意義為單數(shù)）。
1、what, who, which, any, more, all等代詞可以是單數(shù)，也可是復數(shù)，主要靠意思來決定。如：Which is your bag? / Which are your bags? / All is going well. / All have gone to Beijing.
2、表示“時間、重量、長度、價值”等的名詞的復數(shù)作主語時，謂語動詞通常用單數(shù)形式， 這是由于作主語的名詞在概念上是一個整體，如：Thirty minutes is enough for the work.
3、若英語是書名、片名、格言、劇名、報名、國名等的復數(shù)形式，其謂語動詞通常用單數(shù)形式。如： “The Arabian Nights”is an interesting story-book.
4、表數(shù)量的短語“one and a half”后接復數(shù)名詞作主語時，其謂語動詞可用單數(shù)形式（也可用復數(shù)。如：One and a half apples is (are) left on the table.
5、算式中表示數(shù)目（字）的主語通常作單數(shù)看待，其謂語動詞采用單數(shù)形式。如：Twelve plus eight is twenty. / Fifty-six divided by eight is seven.
6、一些學科名詞是以 –ics 結尾，如：mathematics, politics, physics 以及news, works等，都屬于形式上是復數(shù)的名詞，實際意義為單數(shù)名詞，它們作主語時，其謂語動詞要用單數(shù)形式。如：The paper works was built in 1990. / I think physics isn’t easy to study.
7、trousers, glasses, clothes, shoes, 等詞作主語時，謂語用復數(shù)，但如果這些名詞前有a (the) pair of等量詞修飾時，謂語動詞用單數(shù)。如：My glasses are broken. / The pair of shoes under the bed is his.
8、“定冠詞the + 形容詞或分詞”，表示某一類人時，動詞用復數(shù)。
（三）就近一致原則：在英語句子中，有時謂語動詞的人稱和數(shù)與最近的主語保持一致。
1、當兩個主語由either … or, neither … nor, whether … or …, not only … but also連接時，謂語動詞和鄰近的主語一致。如：Either the teacher or the students are our friends. / Neither they nor he is wholly right. / Is neither he nor they wholly right?
2、there be句型be動詞單復數(shù)取決于其后的主語。如果其后是由and連接的兩個主語，則應與靠近的那個主語保持一致。如：There are two chairs and a desk in the room..
注意：Here引導的句子用法同上。
語法經典練習：
1.I, who____ your friend, will try my best to help you with your English.
A.am B.is C.are D.be
2. The rich ____ not always happy.
A.are B.is C.has D.have
3. Neither Tom nor Jack and I ____ his students.
A.are B.am C.is D.was
4. Mary as well as her sisters ____ Chinese in China.
A. are studying B. have studied C. studies D. study
5. Neither my father nor I ____ at home.
A.am B.is C.are D.be
6. Not only my brother but also I ____ good at painting. Both of us ____ good painters.,
A.are;are B.am;am C.ani;are D.is;is
7. Every' boy and every girl ____ to attend the evening party.
A.wish B.wishes C.is like D.like
8. Over 80 percent of the population of China ____ peasants.
A.was B.is C. would be D.are
9. The population of China ____ larger than that of .any other country in the world.
A.is B.are C.has D.have
10. Every means ____ tried but without any result.
A. have been B.is to be C.are to be D. has been
11. Alice, together with two boys,____ for having broken the rule.
A. was punished B. punished C. were punished D. being punished
12. The League secretary and the monitor____ asked to attend the .meeting this afternoon.
A.is B.was C.are D.is being
13. The great writer and professor____.
A. is an old man B. are both old men
C. is an old man and a young man D. were two Chinese
14. There ____ a pen, two pencils and three books on the desk.
A.are B.is C.has D.have
15. A large number of students in our class____ girls.
A. are B. was C. is D. be
16. The number of deer, mountain lions and wild roses ____ much if people leave things as they are.
A. doesn' t change B.don't change C.change D.changed
17. The Arabian Nights ____ well known to the English.
A. is B. are C. was D. were
18. Chairman Mao' s works ____ published.
A. has been B.have been C.was D.is
19. A chemical works____ built there.
A. is to being B.have been C. were to D.has been
20. The Olympic Games ____ held every ____ years.
A.is;four B.are;four C.is;five D.are;five
21 .The United States of America one of the most developed countries in the world.
A.is B.are C.was D.were
22.He is the only one of die students who ____ elected.
A. are B.have C.has D.is
23.Theis is one of the most interesting questions that ____ asked.
A.have B.has C. have been D.has been
24.Many a man ____ come to help us.
A.have B.has C.is D.are
25."All____ present and all____ going on well," our monitor said.
A.is;is B.are;are C.are;is D.is;are
26. The police ____ the murderer everywhere when he suddenly appeared in a theatre.
A. is searching for B. were searching for
C. are searching for D. were searching
27.Your trousers____ dirty.You must have____ washed.
A.is;il B.are;it C.are;them D.is;them
28.This pair of trouseis ____ too long for him.
A.is B.be C.are D.were
29. One and a half bananas ____ left on the table.
A.is B.are C.has D.have
30. Eight times eight ____ sixty - four.
A.is B.are C.get D.equal
Keys:
1~5 AAACA 6~10 CBDAD 11~15 ACABA 16~20 AABDB 21~25 ADCBC
26~30 BCAAA 31~35 ACAAB 36~40 CABBA 41~45 BCCCA 46~50 ADBBC