The words cinque, sink, sync sound the same but have different meanings and spellings. Why do cinque, sink, sync sound the same even though they are completely different words?
The answer is simple: cinque, sink, sync are homophones of the English language.
Games The number five in cards or dice.
A sinkhole.
To descend to the bottom; submerge.
To fall or drop to a lower level, especially to go down slowly or in stages: The water in the lake sank several feet during the long, dry summer.
To subside or settle gradually, as a massive or weighty structure.
Synchronization: "an effect like that of stereo speakers slightly out of sync” ( Time).
Harmony; accord: in sync with today's fashions.
To synchronize.
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").