The "Third Person Singular" refers to the grammatical form used when talking about one person or thing that is not the speaker or the listener. In English, this typically involves using pronouns like he, she, or it. For example, in the sentence "She runs every morning," "she" is the third person singular subject. In addition to pronouns, third person singular verbs often end with an "-s" or "-es" in the present tense. For instance, in the sentence "The dog barks loudly," "barks" is the third person singular form of the verb "to bark." This rule helps clarify who is performing the action in a sentence.