inroad vs usurpation

inroad and usurpation both are nouns.

Word	Noun	Adjective	Verb	Adverb
inroad	Yes	No	No	No
usurpation	Yes	No	No	No

As nouns, usurpation is a hypernym of inroad; that is, usurpation is a word with a broader meaning than inroad:

Other hypernyms of inroad include encroachment, intrusion, trespass, violation.

inroad (noun)	usurpation (noun)
an invasion or hostile attack	wrongfully seizing and holding (an office or powers) by force (especially the seizure of a throne or supreme authority)
an encroachment or intrusion	entry to another's property without right or permission