Subject Verb Agreement

1. All parts of a sentence should agree. In general, if the subject is singular, the verb should be singular; if the subject is plural, the verb should be plural.

Example:

Singular:

The man walks to work.

Plural:

The girls talk at school.

The following indefinite pronouns are singular and almost always take a singular verb form:

“One” words: one, anyone, someone, everyone
“Body” words: nobody, anybody, somebody, everybody
Each, either, neither

The following “group” words, collective nouns, take a singular verb if you are writing of the group as a whole, but they take a plural verb if you are writing of the individuals in the group:

group
committee
crowd
team

band
flock
class
dozen

heap
lot
audience
jury

number
public
none
herd

kind
family

Some nouns are plural in form but singular in meaning and take the singular verb.

Example:

Measles, Mumps, news, mathematics, gallows

Some nouns ending in ics (athletics, politics, acoustics, statistics) are singular when referring to an organized body of knowledge; they are plural when they refer to activities, qualities, or opinions.

Example:

Politics is an interesting field of study.

(Politics here means an organized body of knowledge.)

The politics of a presidential campaign are intense.

(Politics refers to the activities of an election campaign.)

2. When two nouns or constructions are joined by and to form a single unit, that single unit takes a singular verb.

Example:

Peaches and cream is my favorite dessert.

3. When compound subjects are joined by correlatives (two-part connectives: either . . . or; neither . . . nor; not only . . . but) or by or or not, the verb agrees in number with that part of the subject that is closer to the verb.

Example:

Neither Debbie nor her students work on Tuesday.

(Students, the subject closest to the verb, is plural and therefore the verb work is plural.)

4. Be careful when the subject is a word like each, every, none, either, neither, no one, and nobody, especially when followed by a plural object of a preposition.

Example:

Each of the students has a presentation for class.

One of the boys is going to camp this summer.

5. Be careful when several words come between the subject and verb.

Example:

The big dog with the shaggy long hair and floppy ears follows us home.

The ladies from the art class shop at the same store.

6. Be careful when the normal subject-verb order is inverted.

Example:

Over by the fireplace were two chairs.

There were two places set at the long table.

7. Be careful when the subject is a phrase or clause acting as a unit.

Example:

Running a marathon is a great accomplishment.

8. When a clause starts with who, which, or that, the verb agrees with the noun or pronoun to which who, which, or that refers.

Example:

David Pappas is the student who works in the science lab.

(Who refers to the singular student, and works is a singular verb.)

9. Phrases containing mathematical calculations usually take a singular verb.

Example:

Three and three is six. Five times six is thirty.

References:
Aaron, Jane E. The Little, Brown Compact Handbook. 5th ed. New York: Pearson and Longman, 2004.
Glazier, Teresa Ferster. The Least You Should Know about English: Writing Skills. Fort Worth: Harcourt Brace College Publishers, 1994.
McMurray, David. “Subject-verb Agreement.” Power Tools for Technical Communication.
<http://www.io.com/~hcexres/textbook/gram2.html#subjverb>.
Sebranek, Patrick, Verne Meyer, and Dave Kemper. Writers Inc. Burlington, WI: Write Source Educational Publishing House, 1992.
Troyka, Lynn Quitman and Douglas Hesse. Quick Access. 5th ed. Upper River Saddle, New Jersey: Pearson Prentice Hall, 2007.