Happening or done without planning, external cause, or hesitation; done on impulse or naturally.
From Latin 'spontaneus,' derived from 'sponte' meaning 'of one's own will or accord.' The word evolved to describe actions arising from internal motivation rather than external pressure.
In chemistry, 'spontaneous reactions' happen naturally without outside energy—the same root concept that makes humans 'spontaneously' decide to do things, as if by their own nature or will.
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