Two or more nouns joined by and form a plural compound subject, which takes plural verbs. But when a compound subject contains or or nor, the verb should agree with the part of the subject closest to it. Phrases like as well as do not affect grammatical number in formal writing. If the subject they are attached to is singular, it stays singular.
Follow these general rules to correctly use the singular or plural verb with two or more subjects joined by and, or, nor, and expressions like as well as or including:
Two or more nouns joined by the conjunction and usually form a compound subject that is plural. This subject takes plural verbs like are and have, instead of is and has.
Not all words joined by and form a plural. Sometimes, two nouns are together thought of as one unit. Such a compound subject, though it contains and, is singular.
A person’s name and their address are often thought of as one piece of information and can then take a singular instead of plural verb.
— Bertrand Russell, Russell’s Logical Atomism (1918)Also, use a singular verb when a compound subject begins with each or every. (These singular determiners make the subject singular.)
When two or more nouns are joined by or or nor, the verb should agree with the noun closest to it.
Although “his parents” is plural, we use the singular “knows” because the part of the compound subject closest to the verb is “his sister” (his sister knows).
not “neither black nor red are”Since the word closest to the verb is “I,” we match the verb to this subject. Use “have read” (for I have read) instead of “has read.”
TipWith compound subjects, agreement with the verb can sometimes sound odd. For example, because the first phrase in “Either his parents or his sister knows where he is” is plural, using “knows” instead of “know” can sound awkward. Don’t be afraid to rewrite such a sentence.
When an expression like as well as , together with, or including adds to the subject of a sentence, it does not change the number of the subject. If the subject is singular, it stays singular and takes the singular verb.
The subject (flashing red lights) is plural. Use the plural verb warn rather than the singular verb warns.
Note that some writers and speakers feel more comfortable using as well as with plural verbs. This is because of notional agreement : agreement based on actual rather than grammatical number. When using a connective like as well as, you do refer to multiple things or people. Based on meaning rather than grammatical form, using the plural verb is not incorrect.
But grammatically, as well as is not the same as and. It does not form a compound subject: it simply adds to the existing subject. When you have a singular subject in formal usage, use commas to enclose the additional phrase. This will help your readers identify the real subject. Then use the grammatically correct singular verb.
The subject is singular (a large sign). Commas separate the additional phrase from the subject. Use the singular verb warns rather than the plural verb warn.
With a plural subject, don’t use commas around the additional phrase.
Both notional agreement (the number of things being referred to) and the grammatical subject (flashing red lights) indicate use of the plural verb warn.
TipWhen grammatical and notional agreement collide, things can get ugly. If a sentence with as well as sounds awkward, consider rephrasing.
To check whether to use a singular or plural verb with a compound subject in a question , frame the answer. Then use the same verb in the question as you would in the answer.
The answer would be “Tumkin and Maya are . . .” As we know, two nouns joined by and form a plural subject. Since the answer takes “are,” so does the question.
The answer would be “Anita or Lulu is . . .,” since two singular nouns joined by or form a singular compound subject. Use the same verb “is” in the question.
