build up vs train

build up is not a noun while train is a noun.

Word	Noun	Adjective	Verb	Adverb
build up	No	No	Yes	No
train	Yes	No	Yes	No

build up (noun)	train (noun)
	public transport provided by a line of railway cars coupled together and drawn by a locomotive
	wheelwork consisting of a connected set of rotating gears by which force is transmitted or motion or torque is changed
	piece of cloth forming the long back section of a gown that is drawn along the floor
	a series of consequences wrought by an event
	a procession (of wagons or mules or camels) traveling together in single file
	a sequentially ordered set of things or events or ideas in which each successive member is related to the preceding

build up (verb)	train (verb)
form or accumulate steadily	exercise in order to prepare for an event or competition
enlarge, develop, or increase by degrees or in stages	undergo training or instruction in preparation for a particular role, function, or profession
change the use of and make available or usable	create by training and teaching
bolster or strengthen	teach and supervise (someone); act as a trainer or coach (to), as in sports
prepare oneself for a military confrontation	point or cause to go (blows, weapons, or objects such as photographic equipment) towards
	drag loosely along a surface; allow to sweep the ground
	travel by rail or train
	educate for a future role or function
	teach or refine to be discriminative in taste or judgment
	develop (a child's or animal's) behavior by instruction and practice; especially to teach self-control
	cause to grow in a certain way by tying and pruning it