replace vs preempt

replace is not a noun while preempt is a noun.

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

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

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

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

replace (verb)	preempt (verb)
substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)	acquire for oneself before others can do so
put something back where it belongs	make a preemptive bid in the game of bridge
put in the place of another; switch seemingly equivalent items	gain possession of by prior right or opportunity, especially so as to obtain the right to buy (land)
take the place or move into the position of	take the place of or have precedence over