Vocabulary refers to the set of words that a person knows and uses in communication. It includes words used in speaking, writing, and understanding language. A strong vocabulary helps individuals express their thoughts clearly and comprehend what others are saying. It can be built through reading, listening, and practicing language skills. There are two main types of vocabulary: active vocabulary and passive vocabulary. Active vocabulary consists of words that a person uses regularly, while passive vocabulary includes words that a person understands but does not often use. Expanding vocabulary is important for effective communication and can enhance academic and professional success.