Entelechy

En⋅tel⋅e⋅chy:

according to the dictionary:
-a realization or actuality as opposed to a potentiality.
-(in vitalist philosophy) a vital agent or force directing life and growth.



Aristotle puts forward the contrasting concepts of enérgeia and entelécheia in Metaphyics

In Metaphysics, Aristotle states that entelécheia is the fullness of actualization. Energeia is the activity of actualization - or the movement or motion toward actualization not necessarily completed.

Entelechy put another way:

Aristotle claimed that change is the passage from the potential to the actual.

Take this example: a acorn has the potential to become an oak tree. A mature oak tree is the realization of the potential of the the acorn. If you planted an acorn in the middle of an orange grove, it would become an oak tree- not an orange tree. The acorn can't learn to become/become an orange tree- it has to become an oak tree.