1, 2, 3. Three similar terms— homophone, homograph, and homonym —designate words that are identical in pronunciation, spelling, or both, while differing in meaning and usually in origin.
Homophones (“same” + “sound”) are different words that sound alike, whether or not they are spelled alike. Thus pair “two of a kind,” pare “cut off,” and pear, the fruit, are homophones because they sound exactly the same, even though each is spelled differently. But bear “carry or support” and bear, the animal, are homophones that not only sound alike but are also spelled alike.
Homographs (“same” + “writing”) are different words that are spelled the same but may or may not have the same pronunciation. The homographs sound “noise,” sound “healthy,” and sound, “a body of water,” for example, are spelled and pronounced the same way. However, words with the same spelling but different pronunciations are also homographs. Familiar examples are the pairs row rōroʊroh “line” and row rouraʊrou “fight” as well as sewer so̅o̅·ərˈsu ərsoo-er “conduit for waste” and sewer sō·ərˈsoʊ ərsoh-er “person who sews.” Their identical spellings define them as homographs no matter how they are said.
The word homonyms (“same” + “names”) is, strictly speaking, either a synonym for homophones or a name for words that are at once homophones and homographs —alike in both spelling and pronunciation—such as the two words spelled b-e-a-r and the three spelled s-o-u-n-d. As a practical matter, however, the terms homophone, homograph, and homonym are often distinguished from one another by the contexts in which they are found. Homophone and homograph —the first focused on sound and the second on spelling—appear primarily in technical or academic writing, where fine distinctions are important. The more familiar word homonym, heard in classrooms from early grades on, has become an all-inclusive term that describes not only words that are both homophonic and homographic, but words that are either one or the other. In common parlance, then, words that sound alike, look alike, or both, can be called homonyms.