pecking order vs hierarchy

pecking order and hierarchy both are nouns.

Word	Noun	Adjective	Verb	Adverb
pecking order	Yes	No	No	No
hierarchy	Yes	No	No	No

As nouns, pecking order and hierarchy are synonyms defined as:

pecking order and hierarchy: the organization of people at different ranks in an administrative body

Other synonyms of pecking order include power structure.

pecking order (noun)	hierarchy (noun)
the organization of people at different ranks in an administrative body	a series of ordered groupings of people or things within a system
	the organization of people at different ranks in an administrative body