# ψ

 ψ U+03C8, ψ GREEK SMALL LETTER PSI
 ← χ[U+03C7] Greek and Coptic ω →[U+03C9]

## Translingual

### Symbol

ψ

1. (quantum mechanics) a wavefunction
2. (electrical engineering) Electric flux.

#### Usage notes

Some texts use Ψ (uppercase) for the actual wavefunction that appears in the time-dependent Schrödinger equation, and ψ (=ΨeiEt/ħ) (lowercase) for the time-independent spatial wave function that may exist for stationary states (and which then appears in the time-independent Schrödinger equation), but this distinction is not always observed. Otherwise, the distinction may be made by providing the arguments.

## Greek

### Letter

ψ (ps) (lowercase, uppercase Ψ)

1. The lower case letter psi (ψι), the 23rd letter of the modern Greek alphabet.

#### Derived terms

• ψ΄ (ps΄, 700)
• ͵ψ (͵ps, 700,000)