Special Rules of Number and Person
226. When the subject is compound ([§ 38]), the number of the verb is determined by the following rules:—
1. A compound subject with and usually takes a verb in the plural number.
- My brother and sister play tennis.
- The governor and the mayor are cousins.
2. A compound subject with or or nor takes a verb in the singular number if the substantives are singular.
- Either my brother or my sister is sure to win.
- Neither the governor nor the mayor favors this appointment.
3. A compound subject with and expressing but a single idea sometimes takes a verb in the singular number.
The sum and substance [= gist] of the matter is this.
Note. This construction is rare in modern English prose. It is for the most part confined to such idiomatic phrases as end and aim (= purpose), the long and short of it, etc. The poets, however, use the construction freely (as in Kipling’s “The tumult and the shouting dies”).
4. If the substantives connected by or or nor differ in number or person, the verb usually agrees with the nearer.