There are 9 main word classes or parts of speech in English: noun, verb, adjective, adverb, pronoun, preposition, conjunction, determiner, and interjection. Each word class describes the grammatical function that a word performs in a sentence. For example, nouns identify people, places or things, verbs describe actions or states of being, and adjectives describe nouns. Some words can belong to more than one class depending on how they are used.