The words concent, consent sound the same but have different meanings and spellings. Why do concent, consent sound the same even though they are completely different words?
The answer is simple: concent, consent are homophones of the English language.
To give assent, as to the proposal of another; agree. See Synonyms at assent.
Archaic To be of the same mind or opinion.
Acceptance or approval of what is planned or done by another; acquiescence. See Synonyms at permission.
Agreement as to opinion or a course of action: She was chosen by common consent to speak for the group.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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.