The words lea, lee, li sound the same but have different meanings and spellings. Why do lea, lee, li sound the same even though they are completely different words?
The answer is simple: lea, lee, li are homophones of the English language.
A grassland; a meadow.
Nautical The side away from the direction from which the wind blows.
An area sheltered from the wind: in the lee of the boulder.
Nautical Of or relating to the side sheltered from the wind: the lee gunwale.
A traditional Chinese measure of distance, today standardized at 500 meters (547 yards).
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.
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").