Take the subject and verb concord for example. This rule states that a singular subject requires a singular verb, whereas a plural subject should be used with a plural verb.
The boy is rude: ‘’The boy” is a singular subject; “is” is the singular verb. Now, if you should say “The boy are rude,” you’ve violated the rule of concord. This is because you’re using a plural verb with a singular subject. To correct this error, you have to pluralize the subject to correspond with the plural verb: “The boys are rude.”
The subject-verb concord is just one of the numerous rules of concord, all of which are of central importance to accurate communication in English.
For a more detailed audio-visual explanation of the 25 rules of concord with clear examples, watch the following video lecture:
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