The words cist, kissed sound the same but have different meanings and spellings. Why do cist, kissed sound the same even though they are completely different words?
The answer is simple: cist, kissed are homophones of the English language.
A wicker receptacle used in ancient Rome for carrying sacred utensils in a procession.
A stone-lined grave, especially a tomb consisting of a pit lined with stones and often having a lid of stone or wood.
Simple past tense and past participle of kiss.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License 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").