Mathematics, Physics. to restrict (a variable quantity) to discrete values rather than to a continuous set of values.

Physics. to change the description of (a physical system) from classical to quantum-mechanical, usually resulting in discrete values for observable quantities, as energy or angular momentum.

To limit a variable or variables describing a physical system to discrete, distinct values. For example, the energy of electromagnetic radiation such as light at a given frequency must be an integer multiple of hν, where ν is the frequency and h is a Planck's constant; electromagnetic energy is thus inherently quantized (in this case, photons are the quanta of energy). The distinct orbitals of electrons in an atom are also a case of quantized energy. Many apparently continuous phenomena turn out to be quantized at a very fine level or very small scale; quantum mechanics was developed in large part to explain many unexpected cases of quantization in the natural world.