Quantum

Part of speech: noun, adjective

Pronunciation: /ˈkwɒntəm/

Definitions

1. A discrete unit of energy or matter, or relating to the smallest possible amount of a physical quantity
2. A fundamental quantity in physics that denotes the smallest discrete value attainable, often associated with energy or matter and its various properties
3. Referring to the smallest indivisible unit of energy or matter, this term also encompasses the principles governing interactions at atomic and subatomic scales

Etymology: The word "quantum" began as an ordinary Latin question. "Quantus" meant "how much," and its neuter form "quantum" was used as a noun for "an amount" or "how much of something." Medieval Latin writers carried that sense forward, and the word reached English as a plain term for a quantity, a portion, or a share. Its modern meaning came from physics. In 1900, Max Planck proposed that energy is emitted and absorbed in discrete packets, which he called "quanta," the plural of "quantum." The idea was that energy comes in fixed amounts rather than flowing continuously. The old sense of "how much" thus narrowed into a precise unit: the smallest amount of energy that can be exchanged.

Synonyms: amount, portion, measure