The words lice, lyse sound the same but have different meanings and spellings. Why do lice, lyse sound the same even though they are completely different words?
The answer is simple: lice, lyse are homophones of the English language.
Plural of louse.
To undergo or cause to undergo lysis.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.