Before you can do surgery on your writing, though, you need to brush up on your subject-verb anatomy. A singular subject agrees with a singular verb, and a plural subject agrees with a plural verb. A singular subject involves a single item or person: “the rolling gurney” or “a surgical patient.” A plural subject involves more than one item or person: “some badly written hospital signs” or “the shocked copy editors.”
Your subject-verb agreement is most likely fine when the subject is close to the verb, as it is here: “The rolling gurney is about to crash into the unwary sign writer!” The singular subject gurney pairs up with the singular verb is. I’m certain, though, that you sometimes commit a ghastly grammar goof when the subject is far from the verb. Be especially careful of compound subjects, which contain an and. Amnesiac writers forget about the first part of their subject, so they use the wrong verb. This was certainly the problem on Doctor Doofus’ phone system; the compound subject “patience and consideration” belongs with are, not is.
- See more at: http://www.quickanddirtytips.com/education/grammar/subject-verb-agreement#sthash.TljmACR6.dpuf