The words leaches, leeches sound the same but have different meanings and spellings. Why do leaches, leeches sound the same even though they are completely different words?
The answer is simple: leaches, leeches are homophones of the English language.
Plural form of leach.
Third-person singular simple present indicative form of leach.
Plural form of leech.
Third-person singular simple present indicative form of leech.
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.