When two subjects are joined by 'and', the verb is plural: 'John and Mary are coming.' When subjects are joined by 'or' or 'nor', the verb agrees with the nearest subject: 'Either the teacher or the students are responsible' (plural because 'students' is nearest), but 'Either the students or the teacher is responsible' (singular because 'teacher' is nearest). These rules help maintain grammatical agreement even when multiple subjects are involved.
Use clear examples with and, or, and nor to show the pattern. Then present examples where changing the word order changes the verb form to emphasize the proximity rule. Have students create and correct sentences with coordinated subjects.
Students often think that 'or' and 'nor' always require plural verbs, forgetting the proximity rule. Some assume that any coordinated subject always triggers a plural verb. Others struggle with the concept that 'or'/'nor' make the verb agree with only the nearest subject, not both.
You already know the core rule of subject-verb agreement: a singular subject takes a singular verb, and a plural subject takes a plural verb. The complication arises when two subjects are joined by a connector — *and*, *or*, or *nor* — because each connector has different agreement logic. Mastering this requires understanding why the rules are what they are, not just memorizing them.
The *and* rule is intuitive: when you join two subjects with *and*, you are asserting that both are present, creating a compound subject. "John and Mary are coming" — both are coming, so the combined referent is plural. Think of it as addition: one person plus one person equals two people, and two people require a plural verb. Even when both individual subjects are singular, *and* combines them into a plural unit.
The *or* and *nor* rules operate differently because these connectors present alternatives, not combinations. "Either the teacher or the students are responsible" does not assert that both are responsible — it asserts that one or the other is. The speaker is asking the verb to agree with whichever option actually applies. Since you don't know which alternative is real, English uses a pragmatic workaround called the proximity rule: the verb agrees with whichever subject is closest to it. In "either the teacher or the students are responsible," *students* (plural) is nearest to the verb, so *are* is correct. Flip it — "either the students or the teacher is responsible" — and now *teacher* (singular) is closest, so *is* is correct.
This proximity rule can feel arbitrary, but it reflects the architecture of how sentences are processed. By the time a listener or reader reaches the verb, the nearest subject is freshest in working memory. Agreement with the nearest subject is the convention that resolves the otherwise ambiguous case. A useful writing strategy: when the two alternatives are different in number (one singular, one plural), put the plural subject last to avoid the slightly awkward singular verb — "either the manager or the employees are to blame" reads more naturally than "either the employees or the manager is to blame," even though both are grammatically correct.