drop behind vs lag

drop behind is not a noun while lag is a noun.

Word	Noun	Adjective	Verb	Adverb
drop behind	No	No	Yes	No
lag	Yes	No	Yes	No

As verbs, lag is a hypernym of drop behind; that is, lag is a word with a broader meaning than drop behind:

Other hypernyms of drop behind include dawdle, fall back, fall behind.

drop behind (noun)	lag (noun)
	the act of slowing down or falling behind
	one of several thin slats of wood forming the sides of a barrel or bucket
	the time between one event, process, or period and another

drop behind (verb)	lag (verb)
to lag or linger behind	throw or pitch at a mark, as with coins
	cover with lagging to prevent heat loss
	hang (back) or fall (behind) in movement, progress, development, etc.
	lock up or confine, in or as in a jail