The words expedients, expedience sound the same but have different meanings and spellings. Why do expedients, expedience sound the same even though they are completely different words?
The answer is simple: expedients, expedience are homophones of the English language.
Plural form of expedient.
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.