Subject-Verb Agreement
Subjects and verbs must AGREE with one another in number (singular or plural). Thus, if a subject is singular, its verb must also be singular; if a subject is plural, its verb must also be plural.
Basic Rule. A singular subject (she, Bill, car) takes a singular verb (is, goes, shines), whereas a plural subject takes a plural verb.
Example: The list of items is/are on the desk.
If you know that list is the subject, then you will choose is for the verb.
Rule 1. A subject will come before a phrase beginning with of. This is a key rule for understanding subjects. The word of is the culprit in many, perhaps most, subject-verb mistakes.
Hasty writers, speakers, readers, and listeners might miss the all-too-common mistake in the following sentence:
Incorrect: A bouquet of yellow roses lend color and fragrance to the room.
Correct: A bouquet of yellow roses lends . . . (bouquet lends, not roses lend)
Rule 2. Two singular subjects connected by or, either/or, orneither/nor require a singular verb.
Examples:
My aunt or my uncle is arriving by train today.
Neither Juan nor Carmen is available.
Either Kiana or Casey is helping today with stage decorations.
Rule 3. The verb in an or, either/or, or neither/nor sentence agrees with the noun or pronoun closest to it.
Examples:
Neither the plates nor the serving bowl goes on that shelf.
Neither the serving bowl nor the plates go on that shelf.
This rule can lead to bumps in the road. For example, if I is one of two (or more) subjects, it could lead to this odd sentence:
Awkward: Neither she, my friends, nor I am going to the festival.
If possible, it’s best to reword such grammatically correct but awkward sentences.
Better:
Neither she, I, nor my friends are going to the festival.
OR
She, my friends, and I are not going to the festival.
Rule 4. As a general rule, use a plural verb with two or more subjects when they are connected by and.
Example: A car and a bike are my means of transportation.
But note these exceptions:
Exceptions:
Breaking and entering is against the law.
The bed and breakfast was charming.
In those sentences, breaking and entering and bed and breakfast are compound nouns.
Rule 5a. Sometimes the subject is separated from the verb by such words as along with, as well as, besides, not, etc. These words and phrases are not part of the subject. Ignore them and use a singular verb when the subject is singular.
Examples:
The politician, along with the newsmen, is expected shortly.
Excitement, as well as nervousness, is the cause of her shaking.
Rule 5b. Parentheses are not part of the subject.
Example: Joe (and his trusty mutt) was always welcome.
If this seems awkward, try rewriting the sentence.
Rule 6. In sentences beginning with here or there, the true subject follows the verb.
Examples:
There are four hurdles to jump.
There is a high hurdle to jump.
Here are the keys.
Rule 7. Use a singular verb with distances, periods of time, sums of money, etc., when considered as a unit.
Examples:
Three miles is too far to walk.
Five years is the maximum sentence for that offense.
Ten dollars is a high price to pay.
BUT
Ten dollars (i.e., dollar bills) were scattered on the floor.
Rule 8. With words that indicate portions—e.g., a lot, a majority, some, all—Rule 1 given earlier in this section is reversed, and we are guided by the noun after of. If the noun after of is singular, use a singular verb. If it is plural, use a plural verb.
Examples:
A lot of the pie has disappeared.
A lot of the pies have disappeared.
A third of the city is unemployed.
A third of the people are unemployed.
All of the pie is gone.
All of the pies are gone.
Some of the pie is missing.
Some of the pies are missing.
Rule 9. With collective nouns such as group, jury, family, audience, population, the verb might be singular or plural, depending on the writer’s intent.
Examples:
All of my family has arrived OR have arrived.
Most of the jury is here OR are here.
A third of the population was not in favor OR were not in favor of the bill.
Adapted from https://www.grammarbook.com/grammar/subjectVerbAgree.asp
