From Latin 'explanare' (to flatten out) — 'ex-' + 'planus' (flat). Same root as 'plain,' 'plane,' and 'plan.'
To make an idea, situation, or problem clear to someone by describing it in detail or revealing relevant facts or ideas.
From Latin explānāre (to flatten out, to make level, to make clear), from ex- (out, thoroughly) + plānāre (to flatten, to level, to make plain), from plānus (flat, level, clear), from PIE *pleh2- (flat, to spread out). The same PIE root gives Greek platus (broad, flat), Sanskrit prathati (it spreads), and Old English flōr (floor). The original physical sense of spreading something flat was transferred
The word 'planet' is a hidden relative of 'explain.' Greek 'planetes' meant 'wanderer' (from 'planasthai,' to wander), but the underlying concept connects to 'planos' (wandering) and the broader PIE root *pleh₂- (flat, spread). Meanwhile, 'explain' literally means 'to un-fold' or 'to flatten out' — making the crumpled comprehensible by spreading