oppose vs veto

oppose is not a noun while veto is a noun.

Word	Noun	Adjective	Verb	Adverb
oppose	No	No	Yes	No
veto	Yes	No	Yes	No

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

Other hyponyms of oppose include blackball, negative, dissent, protest, resist.

oppose (noun)	veto (noun)
	a vote that blocks a decision
	the power or right to prohibit or reject a proposed or intended act (especially the power of a chief executive to reject a bill passed by the legislature)

oppose (verb)	veto (verb)
be resistant to	command against
be against; express opposition to	vote against; refuse to endorse; refuse to assent
set into opposition or rivalry
fight against or resist strongly
act against or in opposition to
contrast with equal weight or force