pen vs felt-tipped pen

pen and felt-tipped pen both are nouns.

Word	Noun	Adjective	Verb	Adverb
pen	Yes	No	Yes	No
felt-tipped pen	Yes	No	No	No

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

pen: a writing implement with a point from which ink flows
felt-tipped pen: a pen with a writing tip made of felt (trade name Magic Marker)

pen (noun)	felt-tipped pen (noun)
female swan	a pen with a writing tip made of felt (trade name Magic Marker)
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)	felt-tipped pen (verb)
produce a literary work