substitute vs reduce

substitute is a noun but reduce is not a noun.

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

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

substitute: put in the place of another; switch seemingly equivalent items
reduce: simplify the form of a mathematical equation of expression by substituting one term for another

Other hyponyms of substitute include shift, truncate, retool, subrogate.

substitute (noun)	reduce (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

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

substitute (verb)	reduce (verb)
put in the place of another; switch seemingly equivalent items	take off weight
be a substitute	cut down on; make a reduction in
act as a substitute	narrow or limit
	cook until very little liquid is left
	to remove oxygen from a compound, or cause to react with hydrogen or form a hydride, or to undergo an increase in the number of electrons
	make smaller
	reduce in size; reduce physically
	make less complex
	reduce in scope while retaining essential elements
	lessen the strength or flavor of a solution or mixture
	be cooked until very little liquid is left
	be the essential element
	destress and thus weaken a sound when pronouncing it
	undergo meiosis
	reposition (a broken bone after surgery) back to its normal site
	lower in grade or rank or force somebody into an undignified situation
	lessen and make more modest
	simplify the form of a mathematical equation of expression by substituting one term for another
	bring to humbler or weaker state or condition
	put down by force or intimidation