impediment vs difficulty

impediment and difficulty both are nouns.

Word	Noun	Adjective	Verb	Adverb
impediment	Yes	No	No	No
difficulty	Yes	No	No	No

As nouns, difficulty is a hypernym of impediment; that is, difficulty is a word with a broader meaning than impediment:

impediment: something immaterial that interferes with or delays action or progress
difficulty: the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result

Other hypernyms of impediment include difficultness.

impediment (noun)	difficulty (noun)
any structure that makes progress difficult	an effort that is inconvenient
something immaterial that interferes with or delays action or progress	the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result