encroachment vs usurpation

encroachment and usurpation both are nouns.

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

As nouns, encroachment and usurpation are synonyms defined as:

encroachment and usurpation: entry to another's property without right or permission

Other synonyms of encroachment include intrusion, trespass, violation.

encroachment (noun)	usurpation (noun)
entry to another's property without right or permission	wrongfully seizing and holding (an office or powers) by force (especially the seizure of a throne or supreme authority)
influencing strongly	entry to another's property without right or permission
any entry into an area not previously occupied