Origin: 1375–1425; late ME
explanen < L
explānāre to smooth out, make intelligible, spread out on flat surface.
See ex- 1 , plane 1 
Related forms: ex⋅plain⋅a⋅ble, adjective
Synonyms:
1. explicate. Explain, elucidate, expound, interpret imply making the meaning of something clear or understandable. To explain is to make plain, clear, or intelligible something that is not known or understood: to explain a theory or a problem. To elucidate is to throw light on what before was dark and obscure, usually by illustration and commentary and sometimes by elaborate explanation: They asked him to elucidate his statement. To expound is to give a methodical, detailed, scholarly explanation of something, usually Scriptures, doctrines, or philosophy: to expound the doctrine of free will. To interpret is to give the meaning of something by paraphrase, by translation, or by an explanation based on personal opinion: to interpret a poem or a symbol. 4. justify.
Antonyms:
1. confuse.
[ik-spleyn] 