effort vs lost cause

effort and lost cause both are nouns.

Word	Noun	Adjective	Verb	Adverb
effort	Yes	No	No	No
lost cause	Yes	No	No	No

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

effort: a series of actions advancing a principle or tending toward a particular end
lost cause: a defeated cause or a cause for which defeat is inevitable

effort (noun)	lost cause (noun)
earnest and conscientious activity intended to do or accomplish something	a defeated cause or a cause for which defeat is inevitable
use of physical or mental energy; hard work
a notable achievement
a series of actions advancing a principle or tending toward a particular end