reduce vs substitute

reduce is not a noun while substitute is a noun.

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

As verbs, substitute is a hypernym of reduce; that is, substitute is a word with a broader meaning than reduce:

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

Other hypernyms of reduce include exchange, interchange, replace.

reduce (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

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

reduce (verb)	substitute (verb)
take off weight	put in the place of another; switch seemingly equivalent items
cut down on; make a reduction in	be a substitute
narrow or limit	act as a substitute
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