Conventions of Composition Rule 135

Rules: Subject and verb must agree in number.

1. Compound subjects joined by and take a plural verb.
2. Compound subjects joined by or use the verb form of the subject closer to the verb.
3. Plural subjects take a plural verb form, even with singular nouns in intervening phrases.
4. Singular subjects, even if followed by plural nouns in intervening phrases, take the singular verb form. A plural predicate noun after is, was, etc, is correct but often awkward; prefer consists of or some such substitute.
5. Treat as collective nouns (eg. family, jury, team, etc.) as a singular or plural as good sense suggests, but keep the number unchanged throughout the passage.
6. Writers (and speakers) often make subject-verb agreement errors when they begin sentences with "There" is or are. Remember that "There" is not the subject of your sentence. It's an adverb.
7. News, mathematics, physics, economics, etc, are singular. Athletics, statistics, are plural. Politics is singular in the sense of science or career, but plural in the sense of opinions or controversies.

Examples:

Correct: His father and mother are away.

Correct: Either his father or his mother is away.

Correct: The use of so many improbable incidents gives an unrealistic air to the story.

Correct: The ways in which the character treats his parents rudely defy the imagination.

Correct (but awkward): The novel feature of the machine is the powerful rollers that do the grinding.

Better: The novel feature of the machine consists of the powerful rollers that do the grinding.

Correct: The crew was hired a year ago.

Wrong: The crew was eating their dinner.

Better: The crew were eating their dinners.

Wrong: There is a lot of people in that room.

Correct: There are a boy and a girl in that family.

Correct: There is not one single cookie left in the jar.

Practice making the subjects agree with their verbs:

1. Either Robin or our coaches together with the baseball team goes to Deano's after the game.
2. A small percentage of the students leave each weekend for sporting events.
3. Many editors of The Record has won awards for great journalism.
4. After hours of deliberation, the jury doesn't agree with each other about a verdict.

Resources for further explanation of subject-verb agreement:

Purdue OWL's Making Subjects and Verbs Agree

Grammar Book's Subject-Verb Agreement