externality vs external

externality and external both are nouns.

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

externality (noun)	external (noun)
the quality or state of being outside or directed toward or relating to the outside or exterior	outward features

externality (adjective)	external (adjective)
	happening or arising or located outside or beyond some limits or especially surface
	coming from the outside
	from or between other countries
	purely outward or superficial