Compound Subjects: Singular or Plural?

A compound subject is made up of two or more simple subjects joined by a conjunction (such as and, or, or nor):

• books and movies
• cookies or cake
• (not) you nor I
• she and her mother
• South America or Australia

To know whether you should use a singular or plural verb with a compound subject, you need to look at the word that joins the elements of the compound subject.

If they are joined by and, use a plural verb.

• A cat and a dog are walking down the street.
• Cake and ice cream sound delicious.
• Teachers and students ride the bus on field trips.

If they are joined by or, the verb agrees with the element closest to it.

• (Either) Mom or Dad is picking me up today. [Dad is singular, so the verb is singular.]
• A rooster or chickens are making noise in that coop. [Chickens is plural, so the verb is plural.]

If they are joined by nor, the verb agrees with the element closest to it.

• Neither John nor I dance well.
• Neither the teacher nor the students know what the weather will be like next week.

Additionally, if a compound subject is preceded by each or every, the verb should be singular.

• Each student and parent has an appointment with the teacher.
• Every car and truck is inspected by quality control before being sold.

Finally, when a compound subject acts as a single unit (this will be things that are commonly considered one thing, even though they have the structure of "A and B"), use a singular verb.

• Cookies and cream is my favorite ice cream flavor.
• Cops and robbers was a common childhood game when I was a kid.

I hope this helps.