Parts of speech are categories that describe a word’s function in a sentence, such as noun, pronoun, verb, adjective, adverb, preposition, conjunction, and interjection; for example, in the sentence “The happy dog runs quickly and barks loudly under the tree—wow!”—‘dog’ is a noun, ‘happy’ is an adjective, ‘runs’ and ‘barks’ are verbs, ‘quickly’ and ‘loudly’ are adverbs, ‘under’ is a preposition, ‘and’ is a conjunction, and ‘wow!’ is an interjection.
