The phrase the number of requires a singular verb. The phrase a number of requires a plural verb. It may make it easier to distinguish them by understanding that the number of is a (singular) noun phrase that can be the subject of a sentence, while a number of is an adjectival phrase meaning “several.”

The number of frogs in the pond is twice the number of fish.

A number of protestors are gathering outside the capitol building today.

When you see either phrase – the number of , or a number of - disregard the singularity or plurality of the noun following it. If you're having a hard time remembering to do so, try crossing out all information between the "number" phrase and the first verb.

The noun following the number of does not impact the verb because the subject of the sentence is number, which is singular. The noun following a number of will always be plural, because a number of means “several.”

G. Subject / Verb / Object

I. Sample Questions