A part of speech is a category that describes the job a word does in a sentence. Just like players on a sports team have different positions (pitcher, catcher, shortstop), words have different roles to play. The main parts of speech are nouns (words for people, places, things, or ideas), verbs (action or being words), adjectives (words that describe nouns), adverbs (words that describe verbs, adjectives, or other adverbs), pronouns (words that replace nouns), prepositions (words showing relationships like “on,” “under,” or “between”), conjunctions (connecting words like “and” or “but”), and interjections (exclamations like “Wow!”).

Understanding parts of speech helps you see how sentences work. The word “run,” for example, is usually a verb (“I run to school”), but it can also be a noun (“I went for a run”). Knowing which part of speech you're dealing with helps you understand what the word means and how it fits with the other words around it. When teachers diagram sentences or talk about grammar, they're often discussing how different parts of speech work together to create meaning.