Usually, it's pretty clear whether a noun is singular or plural. Some words, however, can be tricky — and figuring out if you should pair a singular or plural verb or pronoun with them is essential. Follow these guidelines for help with singular and plural situations:
Each and every create a singular subject, no matter what they precede, and therefore take a singular verb.
Pronouns containing -body, -thing, and -one (such as everybody, anything, and someone) are singular. They match up with singular verbs and shouldn't pair with the plural pronoun their (a plural).
Companies are singular; they take a singular verb and pronoun (it, not they or their).
In sentences that contain neither/nor or either/or, match the verb to the closest subject.