Nouns themselves do not have a person, as they do not refer to people or other beings capable of grammatical person. However, when we use a noun to refer to a person or entity in a sentence, the verb in that sentence must agree with the person and number of the noun. In English grammar, the third person refers to someone or something that is not the speaker or the listener. For example, in the sentence "John eats apples," John is in the third person because he is not the speaker or the listener. The verb "eats" agrees with the third-person singular subject "John." In summary, the third person is relevant for nouns because it determines the form of the verb that agrees with the noun in a sentence.