Abstract: This chapter discusses the concept of a postulate and develops the basic structure of quantum mechanics using three postulates. Postulate 1 introduces the concept of a quantum state as a solution of the time-independent Schrödinger equation. Postulate 2 introduces observables, which are represented by Hermitian operators; the possible measurement values of an observable are the eigenvalues of the corresponding Hermitian operator. Postulate 3 introduces the concept of a superposition, and the association of the probability for obtaining some measurement result with the complex square of an expansion coefficient in a superposition. In discussing Postulate 3, state normalization, the distinction between discrete and continuous eigenvalues, and the Dirac delta are also introduced.

Keywords: quantum state, Schrödinger equation, observable, Hermitian operator, superposition, Dirac delta,