loop-line vs spur

loop-line and spur both are nouns.

Word	Noun	Adjective	Verb	Adverb
loop-line	Yes	No	No	No
spur	Yes	No	Yes	No

As nouns, spur is a hypernym of loop-line; that is, spur is a word with a broader meaning than loop-line:

loop-line: a railway branch line that branches from the trunk line and then rejoins it later on
spur: a railway line connected to a trunk line

Other hypernyms of loop-line include branch line, spur track.

loop-line (noun)	spur (noun)
a railway branch line that branches from the trunk line and then rejoins it later on	a sharp prod fixed to a rider's heel and used to urge a horse onward
	a railway line connected to a trunk line
	a verbalization that encourages you to attempt something
	tubular extension at the base of the corolla in some flowers
	any sharply pointed projection