spur vs loop-line

spur and loop-line both are nouns.

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

As nouns, loop-line is a hyponym of spur; that is, loop-line is a word with a more specific, narrower meaning than spur:

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

spur (noun)	loop-line (noun)
a sharp prod fixed to a rider's heel and used to urge a horse onward	a railway branch line that branches from the trunk line and then rejoins it later on
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