collar vs ruff

collar and ruff both are nouns.

Word	Noun	Adjective	Verb	Adverb
collar	Yes	No	Yes	No
ruff	Yes	No	Yes	No

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

collar (noun)	ruff (noun)
the act of apprehending (especially apprehending a criminal)	(card games) the act of taking a trick with a trump when unable to follow suit
a figurative restraint	common Eurasian sandpiper; the male has an erectile neck ruff in breeding season
a band that fits around the neck and is usually folded over	a high tight collar
necklace that fits tightly around a woman's neck	an external body part consisting of feathers or hair about the neck of a bird or other animal
a band of leather or rope that is placed around an animal's neck as a harness or to identify it
the stitching that forms the rim of a shoe or boot
a short ring fastened over a rod or shaft to limit, guide, or secure a machine part
anything worn or placed about the neck
(zoology) an encircling band or marking around the neck of any animal