replace vs substitute

replace is not a noun while substitute is a noun.

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

As verbs, replace and substitute are synonyms defined as:

replace and substitute: put in the place of another; switch seemingly equivalent items

Other synonyms of replace include exchange, interchange.

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

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

replace (noun)	substitute (noun)
	a person or thing that takes or can take the place of another
	someone who takes the place of another (as when things get dangerous or difficult)
	an athlete who plays only when a starter on the team is replaced

replace (adjective)	substitute (adjective)
	artificial and inferior
	serving or used in place of another
	capable of substituting in any of several positions on a team

replace (verb)	substitute (verb)
substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)	put in the place of another; switch seemingly equivalent items
put something back where it belongs	be a substitute
put in the place of another; switch seemingly equivalent items	act as a substitute
take the place or move into the position of