moment vs heartbeat

moment and heartbeat both are nouns.

Word	Noun	Adjective	Verb	Adverb
moment	Yes	No	No	No
heartbeat	Yes	No	No	No

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

moment: an indefinitely short time
heartbeat: a very short time (as the time it takes the eye to blink or the heart to beat)

Other hyponyms of moment include blink of an eye, flash, instant, jiffy, New York minute, split second, trice, twinkling, wink.

moment (noun)	heartbeat (noun)
having important effects or influence	an animating or vital unifying force
the n-th moment of a distribution is the expected value of the n-th power of the deviations from a fixed value	the rhythmic contraction and expansion of the arteries with each beat of the heart
a turning force produced by an object acting at a distance (or a measure of that force)	a very short time (as the time it takes the eye to blink or the heart to beat)
a particular point in time
an indefinitely short time
at this time