The words paten, patten sound the same but have different meanings and spellings. Why do paten, patten sound the same even though they are completely different words?
The answer is simple: paten, patten are homophones of the English language.
A plate, usually of gold or silver, that is used to hold the host during the celebration of the Eucharist. Also called patina1.
A plate or shallow dish, especially an artifact from an ancient civilization.
A thin disk of or resembling metal.
Any one of various types of wooden-soled footwear, such as a sandal, shoe, or clog, worn to increase one's height or to keep one's feet out of the mud.
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").