Full Idea
Aristotle sees as the main types of aitia (explanation) those that are also to be construed as the main aspects of the physis (nature) of anything.
Gist of Idea
The four explanations are the main aspects of a thing's nature
Source
report of Aristotle (Physics [c.337 BCE]) by Julius Moravcsik - Aristotle on Adequate Explanations 1
Book Reference
-: 'Synthese' [-], p.6
A Reaction
Interestingly, this suggests that having rejected the Four Causes in favour of the Four Explanations, we might even consider them as the Four Natures, which ties explanation very closely to essence.