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上保持一致，這就叫主謂一致。尋其規律，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、復數形式上保持一致。
1、以單數名詞或代詞、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形式；主語為復數時，謂語動詞用復數形式。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情況用單數形式，但若表語是復數或what從句是一個帶有復數意義的并列結構時，主句的謂語動詞用復數形式。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形式。如：The writer and artist has come.; / ② 由and連接的并列單數主語前如果分別有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，謂語動詞仍用單數形式；若主語為復數，謂語用復數形式。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 +單數名詞和由some, any, no, every構成的復合不定代詞，都作單數看待。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+復數名詞（或代詞）”作主語時，其謂語動詞也可用復數。如：Neither of the texts is (are) interesting. ② 若none of后面的名詞是不可數名詞，它的謂語動詞就要用單數；若它后面的名詞是復數，它的謂語動詞用單數或復數都可以。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，其謂語動詞的數應與句中先行詞的數一致。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；如果它指集體的成員，其謂語動詞就用復數形式。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。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“分數或百分數+名詞”構成的短語作主語，其謂語動詞的數要根據短語中后面名詞的數而定。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”，作定語修飾復數名詞，謂語用復數；the number of“…的數量”，主語是number，謂語用單數。
8、在倒裝句中，謂語動詞的數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必須和主語的意義一致（因有時主語形式為單數，但意義為復數；有時形式為復數，但意義為單數）。
1、what, who, which, any, more, all等代詞可以是單數，也可是復數，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”等的名詞的復數作主語時，謂語動詞通常用單數形式， 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、國名等的復數形式，其謂語動詞通常用單數形式。如： “The Arabian Nights”is an interesting story-book.
4、表數量的短語“one and a half”后接復數名詞作主語時，其謂語動詞可用單數形式（也可用復數。如：One and a half apples is (are) left on the table.
5、算式中表示數目（字）的主語通常作單數看待，其謂語動詞采用單數形式。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的名詞，實際意義為單數名詞，它們作主語時，其謂語動詞要用單數形式。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，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。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。
（三）就近一致原則：在英語句子中，有時謂語動詞的人稱和數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