Psi — ψ Greek Letter Symbol
ψ
Psi — ψ / Ψ
23rd letter of the Greek alphabet · pronounced /saɪ/ or /psaɪ/
PhysicsMathematicsEngineeringQuantum Mechanics
Copy symbol
ψ
Lowercase psi
Ψ
Uppercase Psi
Technical reference
| Unicode (lowercase) | U+03C8 |
| Unicode (uppercase) | U+03A8 |
| HTML entity | ψ |
| HTML decimal | ψ |
| LaTeX | \psi |
| Python / Unicode escape | \u03c8 |
| Alt code (Windows) | Alt + 968 |
Uses in science & engineering
Wave function (quantum mechanics)
Describes the quantum state of a particle. |ψ|² gives the probability density.
\(i\hbar \frac{\partial \psi}{\partial t} = \hat{H}\psi\)
Stream function (fluid mechanics)
Scalar function whose contour lines represent streamlines of a 2D flow field.
\(u = \frac{\partial \psi}{\partial y}, \quad v = -\frac{\partial \psi}{\partial x}\)
Torsion angle (structural engineering)
Angle of twist in a structural member subjected to torsion.
\(\psi = \frac{TL}{GJ}\)
Digamma function (mathematics)
Logarithmic derivative of the gamma function, used in series and integrals.
\(\psi(x) = \frac{d}{dx}\ln\Gamma(x)\)
Related symbols
How to insert in applications
Windows
Best option: copy from this page.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
macOS
Press ⌃⌘Space → Character Viewer → search “psi”
Microsoft Word
Type 03c8 then press Alt+X
Google Docs
Insert → Special characters → search by name
Excel
Insert → Symbol → Subset: Greek → select symbol
LaTeX
Use in math mode: $ … $
Python
Use Unicode escape or chr()
HTML / CSS
Use HTML entity or decimal code