Grammatically Correct: The writer's essential guide to punctuation ...

Agreement Between
Subject and Verb
The dog barks/The dogs bark. He is most hospitable/They are
most hospitable. My class has begun/My classes have begun. Most
nouns, pronouns and verbs have singular and plural forms, and
English speakers are instinctively aware that when a noun or pronoun
is singular, the verb that applies to it is singular; and when
the noun or pronoun is plural, the verb is plural. This is known as
agreement between subject and verb.
When sentences are straightforward, errors in agreement are rare:
Few people would say The dogs barks, He are most hospitable or
My classes has begun. When the structure becomes more complex,
however, mistakes become more likely. The causes fall into two
general categories: uncertainty as to what constitutes the subject,
and so matching the verb to the wrong noun; and uncertainty as to
whether a given subject is in fact singular or plural.
Difficulties in the first category may arise when sentences contain
any of the following:
• Compound subjects
• Alternative subjects
• Distracting parenthetical nouns
• Distracting modifying nouns
• Distracting predicate nouns
• Inverted subject-verb order
Difficulties in the second category may arise when sentences
contain any of the following:
• Collective nouns
• Terms of quantity
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