1. Noun: a word that refers to a person, place, thing, or idea. Examples include "cat," "tree," and "happiness."

1. Pronoun: a word that replaces a noun in a sentence. Examples include "I," "you," and "they."

1. Verb: a word that expresses an action or a state of being. Examples include "run," "think," and "be."

1. Adjective: a word that describes a noun. Examples include "red," "happy," and "heavy."

1. Adverb: a word that describes a verb, adjective, or other adverb. Examples include "quickly," "happily," and "very."

1. Preposition: a word that shows the relationship between a noun or pronoun and other words in a sentence. Examples include "in," "on," and "under."

1. Conjunction: a word that connects clauses or sentences. Examples include "and," "but," and "or."

1. Interjection: a word that expresses strong emotion and is often set off by exclamation points or commas. Examples include "wow," "ouch," and "oh."

1. Article: a word that introduces a noun. There are two articles in English: "a" and "the."

1. Gerund: a verb form that ends in "-ing" and functions as a noun. Examples include "swimming" and "running."