When the persons or things denoted are thought of as individuals, the plural should be used. When the collection is regarded as a unit, the singular should be used.[33]

230. A number in the sense of “several” or “many” regularly takes the plural; the number takes the singular.

231. Half, part, portion, and the like, take either the singular or the plural according to sense.

232. A verb which has for its subject a relative pronoun is in the same person and number as the antecedent. For examples, see [§ 149].

Errors are especially common in such sentences as,—

THE FUTURE TENSE