Quantum

A quantum is the smallest possible, indivisible unit of any physical property, such as energy or light, involved in an interaction. 

Definition and Meaning

In Physics: It refers to discrete quantities rather than a continuous range. For example, light is made of individual packets called photons, which act as quanta of electromagnetic radiation. 
General Meaning: It translates to a quantity, amount, or a distinct share of something. 
Etymology: Most users on Reddit agree that the term was popularized in physics by Max Planck in 1900 when he discovered that energy is emitted in discrete packets. 

Core Concepts in Quantum Science

Quantization:
Properties like energy levels in an electron do not change smoothly; they jump between specific, fixed values.
Superposition: Particles can exist in multiple states or conditions at the same time until they are measured or observed.
Entanglement: Two separate particles can link together so that a change in one instantly affects the other, regardless of distance. 

If you would like to explore further, let me know if you are interested in:

• Quantum computing and how qubits work
• Quantum mechanics history and key experiments
• Practical applications like quantum sensors or cryptography