Improving Your Writing
Agreement
Agreeing means that if the subject of the verb is singular, the verb must have a singular form; likewise if the subject of the verb is plural, the verb must have a plural form. For example, we say ‘he sings’ (singular subject, singular verb form) and ‘they sing’ (plural subject, plural verb form). ‘He sing’ and ‘they sings’ are incorrect because they mix singular and plural forms.
This example is a very easy one, but sometimes problems with agreement can be harder to spot.