Pivotal describes something extremely important because other things depend on it or turn around it.
From 'pivot', a French word meaning 'hinge, point on which something turns', plus the suffix '-al'. It turned from a physical turning point into a metaphorical one.
A 'pivotal' moment is literally a hinge in your life story; after it, the direction changes. Once you see it that way, you can spot the little decisions that quietly become huge hinges later.
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