In physics, a very small and specific amount of energy or matter; more generally, a quantity or amount of something.
From Latin *quantum* meaning 'how much' or 'as much as'. In the 20th century, physics borrowed it to describe the smallest possible packets of energy or matter.
Quantum sounds futuristic, but it literally just means 'how much'. Quantum physics is weird not because it’s magical, but because at tiny scales, nature only allows certain exact 'amounts' of energy and no in‑betweens.
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