periphery vs outer boundary

periphery and outer boundary both are nouns.

Word	Noun	Adjective	Verb	Adverb
periphery	Yes	No	No	No
outer boundary	Yes	No	No	No

As nouns, periphery and outer boundary are synonyms defined as:

periphery and outer boundary: the outside boundary or surface of something

Other synonyms of periphery include fringe.

periphery (noun)	outer boundary (noun)
the outside boundary or surface of something	the outside boundary or surface of something