moment vs eleventh hour

moment and eleventh hour both are nouns.

Word	Noun	Adjective	Verb	Adverb
moment	Yes	No	No	No
eleventh hour	Yes	No	No	No

As nouns, eleventh hour is a hyponym of moment; that is, eleventh hour is a word with a more specific, narrower meaning than moment:

moment (noun)	eleventh hour (noun)
having important effects or influence	the latest possible moment
the n-th moment of a distribution is the expected value of the n-th power of the deviations from a fixed value
a turning force produced by an object acting at a distance (or a measure of that force)
a particular point in time
an indefinitely short time
at this time