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