Learner's definition of EXPLANATION
1 [noncount] : the act or process of making something clear or easy to understand : the act or process of telling, showing, or being the reason for or cause of something
She declined the offer without (further) explanation.
Some of his actions defy explanation. [=cannot be explained]
The company offered little by way of explanation for the delays. [=as a way of explaining why there were delays]
2 [count] : something (such as a statement or fact) that explains something — often + for or of
Did the company offer an explanation for the delays?
There are several possible explanations for the current oil shortage.
a likely/probable/possible/plausible explanation of how the accident occurred