A grammar error occurs when the rules of a language are not followed, leading to incorrect sentence structure or word usage. These errors can include mistakes in verb tense, subject-verb agreement, punctuation, and word choice. For example, saying "She go to the store" instead of "She goes to the store" is a common grammar error. Grammar errors can affect the clarity and professionalism of written and spoken communication. They can confuse the reader or listener, making it difficult to understand the intended message. Correcting these errors is essential for effective communication in both personal and professional contexts, such as in academic writing or business correspondence.