Quantization: Something which is quantized is split into discrete levels, ie: if a something is quantised, it may only have a few discrete values, rather than a continious spectrum of possibilities.

Quantum number: A number which labels the quantum state of a system, and thus which may determine various properties of that system. There are principal, orbital angular momentum, magnetic angular momentum, and spin angular momentum quantum numbers.

Quaternary: A quaternary carbon (or nitrogen) is one which is attached to four other carbon atoms.