Full Idea
If we can distinguish the different kinds of change (alteration, locomotion, growth, diminution), then we can say that a given attribute is essential to an object if its loss would result in the destruction of that object.
Gist of Idea
Within the four types of change, essential attributes are those whose loss means destruction
Source
Irving M. Copi (Essence and Accident [1954], p.707-8)
Book Reference
-: 'Journal of Philosophy' [-], p.707
A Reaction
As Copi is aware, this is a necessary condition for a property for essence, but not sufficient. If an attribute were necessary but non-essential, its loss would also be destruction. We say the essential attributes must also have some explanatory role.