The sentence “She laugh at everybody” is grammatically incorrect because the verb does not agree with its subject. The correct sentence is “She laughs at everybody.” This error can be explained through the rules of subject–verb agreement in the structure of English. In English, the form of the verb in the simple present tense changes according to the subject. When the subject is a first-person or second-person pronoun such as “I” or “you,” or a plural noun such as “they” or “students,” the base form of the verb is normally used. For example, “I laugh,” “you laugh,” and “they laugh.” However, when the subject is a third-person singular noun or pronoun, such as “he,” “she,” “it,” or “the girl,” the verb generally takes the suffix “-s” or “-es.” Therefore, we say “She laughs,” “He works,” “It moves,” and “The girl sings.” In the given sentence, “She” is a third-person singular subject. The verb “laugh” must therefore be changed to “laughs.” The correct grammatical structure is: Subject + Verb +