Chemically speaking, vinegar is acidic because it contains acetic acid. According to the theory of acid-base system, vinegar is neutral, because the theory of acid-base system says that foods containing more sulfur, phosphorus, and chlorine are considered acidic. But the founder of the acid-base system theory has been taken to court, and this theory is basically a fraud, so we only analyze it from a chemical point of view, that is, vinegar is acidic.