pair of pliers vs pliers

pair of pliers and pliers both are nouns.

Word	Noun	Adjective	Verb	Adverb
pair of pliers	Yes	No	No	No
pliers	Yes	No	No	No

As nouns, pair of pliers and pliers are synonyms defined as:

pair of pliers and pliers: a gripping hand tool with two hinged arms and (usually) serrated jaws

Other synonyms of pair of pliers include plyers.

pair of pliers (noun)	pliers (noun)
a gripping hand tool with two hinged arms and (usually) serrated jaws	a gripping hand tool with two hinged arms and (usually) serrated jaws