The homonym can be viewed as a subset of homographs. The homonym can also be considered a subset of homophones. While homograph means words that are spelled the same, and homophone means words that sound the same, homonym means words that have both the same sound and spelling, but are different words. Let’s use some examples to clarify the differences between a homonym and these other two similar concepts.
Homographs that are not homonyms include words like read meaning the present tense of the verb "to read" and read representing the past tense of the same verb. Since these two words, although they are spelled the same, are pronounced differently, they are homographs, but not homonyms.
Homophones that are not homonyms include words like peer, meaning "equal," and pier, meaning a place to dock a boat. Since these two words are pronounced identically but do not have the same spelling, they are homophones, but not homonyms.
And a third example of words that might seem to be homonyms but aren’t are multiple meaning words: words with the same root, but with various incarnations as, perhaps, a noun and a verb. Since these are actually just the same word used in different ways, they don’t meet the criteria for homonyms. But if we take the words peer meaning “a person of equal standing” and peer meaning “look intently,” then we have two distinct words that both have the same spelling and the same sound, and this is an example of a homonym.
Homographs confuse people, because sometimes the same spelling has multiple pronunciations, and you have to scope out which meaning is being referenced before you know how to pronounce it. Homophones confuse people because the identical sound gives them close identification in our minds, and if we mismatch spelling with meaning, then we end up with typos. Homonyms don’t have either of these problems: since they have identical spellings and identical sounds, unless there are other homophones with different sounds or homographs with different spellings involved, it’s really difficult to make a mistake with them.