internal vs interior

internal is not a noun while interior is a noun.

Word	Noun	Adjective	Verb	Adverb
internal	No	Yes	No	No
interior	Yes	Yes	No	No

As adjectives, internal and interior are synonyms defined as:

Other synonyms of internal include home, national.

As adjectives, internal and interior are synonyms defined as:

Other synonyms of internal include inner.

internal (noun)	interior (noun)
	the inner or enclosed surface of something
	the region that is inside of something

internal (adjective)	interior (adjective)
happening or arising or located within some limits or especially surface	situated within or suitable for inside a building
inside the country	inside the country
occurring within an institution or community	of or coming from the middle of a region or country
innermost or essential	inside and toward a center
located inward	located inward