usurp vs usurpation

usurp is not a noun while usurpation is a noun.

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

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

usurp (verb)	usurpation (verb)
seize and take control without authority and possibly with force; take as one's right or possession
take the place of