pliers vs pair of pliers

pliers and pair of pliers both are nouns.

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

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

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

Other synonyms of pliers include plyers.

pliers (noun)	pair of 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