Compound subjects and verb agreement

A subject with two or more nouns joined by the word and is called a compound subject. A compound subject takes a plural verb, even if some or all of the nouns are singular. Here are some examples of compound subjects joined by and:

• My mother and I are going to the store. (Even though my mother and the pronoun I are both singular, together they take the plural verb are.)
• The two kittens and the mother cat are hiding in the room. (Kittens is plural and cat is singular, and the verb is plural.)
• Jonah, Pat, and Kelly run two miles a day. (No matter how many singular nouns are joined together, the verb is plural.)

Sometimes the nouns in a compound subject are joined by or. If all the nouns are singular, the verb is also singular. If all of the nouns are plural, the verb is also plural. Here are some examples of compound subjects joined by or:

• Either Jess or Taylor takes out the garbage. (Both nouns are singular and the verb is singular.) 
• Their parents or grandparents drop them off in the mornings. (Both nouns are plural and the verb is plural.)
• An apple, an orange, or a banana is served with lunch each day. (All nouns are singular, and the verb is singular.)

If one of the nouns is plural and another is singular, the choice between a singular or plural verb depends on context and personal habit. The grammar rule that many teachers and grammarians teach is that the verb agrees with the noun closest to it, but in actual usage, this rule is often broken.

Therefore, in formal writing, a sentence like the one below would probably be written with the singular verb is, but in actual conversation you would be just as likely to hear someone use the plural verb are—and no one would notice.

• Usually taxes or the economy is/are discussed at length in his meetings.

I hope this is helpful.