The words chiton, kitten sound the same but have different meanings and spellings. Why do chiton, kitten sound the same even though they are completely different words?
The answer is simple: chiton, kitten are homophones of the English language.
Any of various marine mollusks of the class Polyplacophora that live on rocks and have shells consisting of eight overlapping calcareous plates. Also called sea cradle.
A tunic worn by men and women in ancient Greece.
A young cat.
To bear kittens.
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").