noun
quantum
KWON-tuhm
noun
1
The smallest discrete amount of something, especially a fixed unit of energy in physics.
"A photon is a quantum of light."
"Energy at this scale moves in quanta, not smooth increments."
adj
1
Involving quantum mechanics — the physics of matter and energy at the atomic and subatomic scale.
"Quantum computers use particles that can exist in more than one state at once."
"The professor's research focuses on quantum theory."
2
Sudden and dramatic rather than gradual — used loosely for a major leap forward.
"The new engine was a quantum leap in efficiency."
"Her career took a quantum jump after the promotion."
How to Use Quantum
Learner’s notesIn plain EnglishA fixed, indivisible unit — in everyday use, often shorthand for "a huge, sudden jump" (a quantum leap).
Common mistake
"Quantum leap" is popularly used to mean a huge change, but in physics a quantum jump is actually the smallest possible change — the opposite of huge.
Common pairings
quantum leap
quantum mechanics
quantum computer
quantum physics
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A photon is a _____ of light.
Etymology
From Latin quantum, "how much" — the neuter form of quantus.