The words chordate, cordate sound the same but have different meanings and spellings. Why do chordate, cordate sound the same even though they are completely different words?
The answer is simple: chordate, cordate are homophones of the English language.
Any of numerous animals belonging to the phylum Chordata, having at some stage of development a dorsal nerve cord, a notochord, and gill slits and including all vertebrates and certain marine animals, such as the lancelets.
Having a heart-shaped outline: a cordate leaf.
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").