decrement vs free fall

decrement and free fall both are nouns.

Word	Noun	Adjective	Verb	Adverb
decrement	Yes	No	No	No
free fall	Yes	No	No	No

As nouns, free fall is a hyponym of decrement; that is, free fall is a word with a more specific, narrower meaning than decrement:

Other hyponyms of decrement include dip, drop, fall, shrinkage.

decrement (noun)	free fall (noun)
the amount by which something decreases	a sudden sharp decrease in some quantity
a process of becoming smaller or shorter	the ideal falling motion of something subject only to a gravitational field