obstruction vs impediment

obstruction and impediment both are nouns.

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

As nouns, obstruction and impediment are synonyms defined as:

Other synonyms of obstruction include impedimenta, obstructer, obstructor.

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

obstruction: something immaterial that stands in the way and must be circumvented or surmounted
impediment: something immaterial that interferes with or delays action or progress

Other hypernyms of obstruction include balk, baulk, check, deterrent, handicap, hinderance, hindrance.

obstruction (noun)	impediment (noun)
getting in someone's way	any structure that makes progress difficult
the act of obstructing	something immaterial that interferes with or delays action or progress
any structure that makes progress difficult
something immaterial that stands in the way and must be circumvented or surmounted
the physical condition of blocking or filling a passage with an obstruction