trail vs drop behind

trail is a noun but drop behind is not a noun.

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

As verbs, trail and drop behind are synonyms defined as:

Other synonyms of trail include drag, drop back, get behind, hang back.

trail (noun)	drop behind (noun)
a path or track roughly blazed through wild or hilly country
evidence pointing to a possible solution
a track or mark left by something that has passed

trail (verb)	drop behind (verb)
drag loosely along a surface; allow to sweep the ground	to lag or linger behind
hang down so as to drag along the ground
go after with the intent to catch
move, proceed, or walk draggingly or slowly
to lag or linger behind