In physics and chemistry, a quantum is a discrete packet of energy or matter. The term quantum also means the minimum value of a physical property involved in an interaction. The plural of quantum is quanta.
Key Takeaways: Quantum Definition
- In chemistry and physics, quantum refers to a single packet of matter or energy.
- In practical use, it refers to the minimum amount of energy required for a change or the minimum value of any physical property in an interaction.
- Quantum is the singular form of the word. Quanta is the plural form of the term.
For example: the quantum of charge is the charge of an electron. Electric charge can only increase or decrease by discrete energy levels. So, there is no half-charge. A photon is a single quantum of light. Light and other electromagnetic energy is absorbed or emitted in quanta or packets.
The word quantum comes from the Latin word quantus, which means "how great." The word came into use before the year 1900, in reference to quantum satis in medicine, which means "the amount which is sufficient".
Misuse of Term
The word quantum is often mis-used as an adjective to mean the opposite of its definition or in an inappropriate context. For example, the term "quantum mysticism" implies a correlation between quantum mechanics and parapsychology that has not been supported by empirical data. The phase "quantum leap" is used to suggest a large change, while the definition of quantum is that the change is the minimum amount possible.