The words quince, quints sound the same but have different meanings and spellings. Why do quince, quints sound the same even though they are completely different words?
The answer is simple: quince, quints are homophones of the English language.
A western Asian shrub or tree (Cydonia oblonga) having white flowers and hard applelike fruit.
The aromatic, many-seeded fruit of this plant, edible only when cooked.
Plural form of quint.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").