external vs internal

external is a noun but internal is not a noun.

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

external (noun)	internal (noun)
outward features

external (adjective)	internal (adjective)
happening or arising or located outside or beyond some limits or especially surface	happening or arising or located within some limits or especially surface
coming from the outside	inside the country
from or between other countries	occurring within an institution or community
purely outward or superficial	innermost or essential
	located inward