pillow vs long pillow

pillow and long pillow both are nouns.

Word	Noun	Adjective	Verb	Adverb
pillow	Yes	No	Yes	No
long pillow	Yes	No	No	No

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

pillow: a cushion to support the head of a sleeping person
long pillow: a pillow that is often put across a bed underneath the regular pillows

Other hyponyms of pillow include bed pillow, bolster.

pillow (noun)	long pillow (noun)
a cushion to support the head of a sleeping person	a pillow that is often put across a bed underneath the regular pillows

pillow (verb)	long pillow (verb)
rest on or as if on a pillow