pen vs cattle pen

pen and cattle pen both are nouns.

Word	Noun	Adjective	Verb	Adverb
pen	Yes	No	Yes	No
cattle pen	Yes	No	No	No

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

pen (noun)	cattle pen (noun)
female swan	a pen for cattle
a writing implement with a point from which ink flows
an enclosure for confining livestock
a correctional institution for those convicted of major crimes
a portable enclosure in which babies may be left to play

pen (verb)	cattle pen (verb)
produce a literary work