What is a subject and a verb agreement?

Answer 1

Subject and verb are in agreement when the subject and verb have the same grammatical "number", either singular or plural. One of the most common mistakes in subject-verb agreement occurs when the subject is a compound of two individually singular subjects, as in "Mary and Jane". This is a plural subject. Another common mistake occurs when the subject is either singular or plural but a prepositional phrase with an object of opposite number appears in the sentence before the verb; it is easy for careless speakers/writers to make the verb agree with the object of the preposition rather than the true subject. An example is, "The girl with the green shoes is [not are!] my cousin."

Answer 2

Subject-verb agreement means that the subject and the verb in a sentence must correspond in number. For example, a singular subject (e.g., "he") should have a singular verb (e.g., "is"), while a plural subject (e.g., "they") should have a plural verb (e.g., "are"). This agreement helps to ensure that the sentence is grammatically correct and clear.