a discrete amount of something that is analogous to the quantities in quantum theory
"The new software update requires a minimum quantum of server resources before it can process large datasets efficiently."
(physics) the smallest discrete quantity of some physical property that a system can possess (according to quantum theory)
"The experiment revealed that energy is not continuous but exists in distinct packets known as quanta."
The total amount of something; quantity.
"The quantum of rain that fell last night was enough to flood the basement."
In plain English: A quantum is the smallest possible amount of something that can exist, like a single packet of energy.
"The quantum of energy released by the atom was far smaller than anyone expected."
Of a change, sudden or discrete, without intermediate stages.
"The stock price didn't slowly decline; it dropped in a quantum leap overnight after the scandal broke."
In plain English: Quantum means relating to extremely small amounts of energy that can only be measured in specific, separate units rather than continuous flows.
"The company made a quantum leap in its technology this year."
Usage: Use this adjective to describe changes that happen instantly in distinct steps rather than gradually over time. It is most often applied to physics concepts but can metaphorically characterize any abrupt shift with no middle ground.
The word comes from Late Latin quantum, which is the neuter form of the Latin adjective meaning "how much." It entered English in the early 20th century to describe the smallest possible discrete unit of any physical property.