underclassman vs soph

underclassman and soph both are nouns.

Word	Noun	Adjective	Verb	Adverb
underclassman	Yes	No	No	No
soph	Yes	No	No	No

As nouns, soph is a hyponym of underclassman; that is, soph is a word with a more specific, narrower meaning than underclassman:

Other hyponyms of underclassman include fresher, freshman, junior, sophomore.

underclassman (noun)	soph (noun)
an undergraduate who is not yet a senior	a second-year undergraduate