The words miscible, missable sound the same but have different meanings and spellings. Why do miscible, missable sound the same even though they are completely different words?
The answer is simple: miscible, missable are homophones of the English language.
Chemistry That can be mixed in all proportions. Used of liquids.
Able to avoid detection.
Far from unmissable; not worth watching or experiencing.
Capable of being missed.
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").