The words ascent, assent sound the same but have different meanings and spellings. Why do ascent, assent sound the same even though they are completely different words?
The answer is simple: ascent, assent are homophones of the English language.
The act or process of rising or going upward.
An advancement, especially in social status.
An upward slope or incline.
A going back in time or upward in genealogical succession.
To agree, as to a proposal; concur.
Agreement; concurrence: reached assent on a course of action.
Acquiescence; consent: gave my assent to the plan.
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.