主謂一致即句子的主語和謂語在人稱和數上保持一致。一般說來，主語的單、複數形式決定著謂語動詞應採取的相應形式。在實際應用中，有時情況較為複雜，但在現代英語中基本遵循如下原則：語法一致原則、意義一致原則和就近原則。
語法一致原則語法一致原則就是根據主語的語法形式決定其謂語動詞的語法形式。主語是單數，謂語動詞就用單數形式;主語是複數，謂語動詞就用複數形式。例如：
A letter has been sent to every student.
Two letters have been sent to every student.
To treat them in that way is unfair.
Smoking cigarettes is dangerous to your health.
意義一致原則意義一致原則指主謂之間的一致關係不是由主語的語法形式來決定，而是由主語所表達的意義來決定。形式是單數的主語，其謂語可能是複數形式;反之，形式是複數的主語，其謂語有可能是單數。例如：
The class are doing experiment on heat and light.
The team are playing magnificently.
The United States is a country advanced in science and technology.
Ten dollars is all I have left.
Two thirds of the area is under water.
同一單詞作主語，根據其表達意義的不同，有時用單數動詞，有時卻要用複數動詞。例如：
The family is the basic unit of the society.
The family have agreed among themselves to spend their vacation in Italy.
就近原則就近原則是指謂語動詞與它最近的名詞、代詞或其他詞在人稱或數上保持一致。常見於either … or, neither … nor等並列結構或there, here引起的句子中。例如：
Either you or he was wrong.
There is a pen, a few envelopes and some paper in the drawer.
Not only his children but he himself is hoping to be there.
上述三條原則的具體應用比較複雜，以下幾點需要特別注意。我們分三大類情況來看：
1. 謂語動詞用單數的情況1)one, each, every, everyone, everybody, no, no one, one of, many a, either, neither, nobody, anyone, somebody, someone等作主語或主語修飾語時，謂語動詞用單數。例如：
Every boy and girl is treated in the same way.
Neither of them drinks coffee.
Each man and (each) woman has good reason to be proud of the work done by their fathers.
2)a kind of, a sort of, a portion of, a section of, a series of, a succession of, a pair of, a couple of等修飾主語時，謂語動詞一般根據語法一致原則用單數。例如：
A pair of scissors is what he needs now.
A series of lectures on radio engineering is scheduled.
There is a couple of vacant rooms behind the office.
3)表示國家、單位、書報等名稱或表示時間、距離、體積、度量衡(將其視為一整體)等的名詞或短語作主語時，謂語動詞用單數。例如：
The Netherlands is famous for its tulips.
One hundred miles is too far to travel on foot.
Ten pounds was missing from the bill.
The Thirty-Nine Steps is an interesting novel.
4)不定式、動名詞短語或名詞性從句作主語時，謂語動詞也要用單數。例如：
To master at least a foreign language is very necessary in the present conditions.
Forgetting the past means nothing but betrayal.
When they will start on their journey hasn’t been decided.
5)單數詞作主語，雖然後接由including, as well as, together with, in addition to, accompanied by等詞或短語連接其他的詞，謂語動詞仍然用單數。例如：
Gold, as well as silver, ahs recently risen in price.
The factory, with all its equipment, has been burned.
John together with his brother has gone to the party.
2. 謂語動詞用複數的情況1)both, some, few, many, several, the majority (of), the minority (of)等詞語作主語或主語修飾語時，謂語動詞用複數。例如：
Both of them have gone to Shanghai on business.
Few of my classmates really understand me.
The majority of (the) doctors believe smoking is harmful to health.
2)以複數形式結尾的山脈、群島、瀑布等專有名詞作主語時，謂語動詞用複數。例如：
The Niagara Falls are very spectacular.
The Philippines are in the Pacific Ocean.
3)表示群體或類屬的「the + 形容詞」作主語時，謂語動詞用複數。例如：
The injured were sent to hospital at once.
In many western films, the good are well rewarded and the bad are punished.
3. 謂語動詞的單、複數要視情形而定的情況1)由and 連接兩個主語時，謂語動詞一般用複數。例如：
Your problem and mine are similar.
但當and連接的詞語作整體考慮，指同一人、同一事物或概念時，謂語動詞用單數。例如：
The worker and poet has published a collection of poems recently.
Too much work and too little rest often leads to illness.
當and連接兩個形容詞修飾一個單數名詞作主語時，如果指一件事物謂語動詞用單數;如果指兩件事物則謂語動詞用複數。例如：
A black and white (黑白相間) horse was trotting down.
The red and the yellow rose are both beautiful.
2)集合名詞如family, group, team, the public, crowd, committee, staff等作主語，表整體意義時謂語動詞用單數;表個體意義時用複數。例如：
Our team has won the game.
Our team are discussing about how to win.
3)一些表示數量的短語如a lot of, any of, most of, half of, two-thirds of, eighty percent of, part of, the rest of, some of, none of, all of等與名詞連用時，後面名詞用單數則謂語動詞用單數;名詞用複數，謂語動詞也用複數。例如：
A large percentage of our pilots retire early.
A large percentage of his income is paid in income tax.
Most of the book is interesting.
Most of the books are informative though a little dull.
4)另一些表示數量的短語如a number of, a total of, an average of等後接複數名詞，謂語動詞用複數;但其中不定冠詞換成定冠詞時，謂語動詞要用單數。例如：
A number of students were late for school owing to the storm.
The number of jobs is increasing.
An average of 3000 letters a month are received by the newspaper’s office.
The average of letters received each month is 3000.