supersede vs preempt

supersede is not a noun while preempt is a noun.

Word	Noun	Adjective	Verb	Adverb
supersede	No	No	Yes	No
preempt	Yes	No	Yes	No

As verbs, preempt is a hyponym of supersede; that is, preempt is a word with a more specific, narrower meaning than supersede:

Other hyponyms of supersede include deputise, deputize, step in, substitute, displace, usurp, oust.

supersede (noun)	preempt (noun)
	a high bid that is intended to prevent the opposing players from bidding

supersede (verb)	preempt (verb)
take the place or move into the position of	acquire for oneself before others can do so
	make a preemptive bid in the game of bridge
	gain possession of by prior right or opportunity, especially so as to obtain the right to buy (land)
	take the place of or have precedence over