voltage drop vs free fall

voltage drop and free fall both are nouns.

Word	Noun	Adjective	Verb	Adverb
voltage drop	Yes	No	No	No
free fall	Yes	No	No	No

As nouns, free fall is a hypernym of voltage drop; that is, free fall is a word with a broader meaning than voltage drop:

voltage drop: a decrease in voltage along a conductor through which current is flowing
free fall: a sudden sharp decrease in some quantity

Other hypernyms of voltage drop include dip, drop, fall.

voltage drop (noun)	free fall (noun)
a decrease in voltage along a conductor through which current is flowing	a sudden sharp decrease in some quantity
	the ideal falling motion of something subject only to a gravitational field