The words knits, nits sound the same but have different meanings and spellings. Why do knits, nits sound the same even though they are completely different words?
The answer is simple: knits, nits are homophones of the English language.
Third-person singular simple present indicative form of knit.
Small particles of ore.
Plural form of nit.
Definitions 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.