leash vs collar

leash and collar both are nouns.

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

As nouns, leash and collar are synonyms defined as:

leash (noun)	collar (noun)
a figurative restraint	the act of apprehending (especially apprehending a criminal)
restraint consisting of a rope (or light chain) used to restrain an animal	a figurative restraint
the cardinal number that is the sum of one and one and one	a band that fits around the neck and is usually folded over
	necklace that fits tightly around a woman's neck
	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