As nouns the difference between eternality and externality
is that eternality
is the condition of being eternal; endlessness while externality
is (uncountable) the state of being external or externalized.
The condition of being eternal; endlessness
All of time; eternity
(uncountable) The state of being external or externalized.
(countable) A thing that is external relative to something else.
(economics, countable) An impact, positive or negative, on any party not involved in a given economic transaction or act.
* network externality