Different authors may have different definitions for the same term. The discussions are restricted to Schrödinger picture and non-relativistic quantum mechanics. Notation: | x ⟩ {\displaystyle |x\rangle } - position eigenstate | α ⟩ , | β ⟩ , | γ ⟩ . . . {\displaystyle |\alpha \rangle ,|\beta \rangle ,|\gamma \rangle ...} - wave function of the state of the system Ψ {\displaystyle \Psi } - total wave function of a system ψ {\displaystyle \psi } - wave function of a system (maybe a particle) ψ α ( x , t ) {\displaystyle \psi _{\alpha }(x,t)} - wave function of a particle in position representation, equal to ⟨ x | α ⟩ {\displaystyle \langle x|\alpha \rangle }