Plural nouns refer to more than one person, place, thing, or idea, like "cats" or "cities." Most are formed by adding -s or -es (e.g., dog → dogs, box → boxes). For irregular nouns, like "child" (children) or "mouse" (mice), memorizing exceptions is key. As an English tutor, I recommend practicing with varied examples to master plural noun forms for clear communication in writing and speaking.