effort vs stab

effort and stab both are nouns.

Word	Noun	Adjective	Verb	Adverb
effort	Yes	No	No	No
stab	Yes	No	Yes	No

As nouns, stab is a hyponym of effort; that is, stab is a word with a more specific, narrower meaning than effort:

effort: earnest and conscientious activity intended to do or accomplish something
stab: informal words for any attempt or effort

effort (noun)	stab (noun)
earnest and conscientious activity intended to do or accomplish something	a strong blow with a knife or other sharp pointed instrument
use of physical or mental energy; hard work	informal words for any attempt or effort
a notable achievement	a sudden sharp feeling
a series of actions advancing a principle or tending toward a particular end