subcontract vs undertake

subcontract is a noun but undertake is not a noun.

Word	Noun	Adjective	Verb	Adverb
subcontract	Yes	No	Yes	No
undertake	No	No	Yes	No

subcontract (noun)	undertake (noun)
a contract assigning to another party some obligations of a prior contract

subcontract (verb)	undertake (verb)
work under a subcontract; engage in a subcontract	promise to do or accomplish
arranged for contracted work to be done by others	enter into a contractual arrangement
	enter upon an activity or enterprise
	accept as a charge
	accept as a challenge