Psi (Ψ, ψ)
Quick Info
- Pronunciation: SIGH
- English: ps
- Common Use: Wave function
Historical Background
Twenty-third letter of the Greek alphabet, derived from Phoenician letter "qoph", meaning cord. The symbol Ψ has become particularly significant in quantum mechanics, where it represents the wave function, a fundamental concept introduced by Erwin Schrödinger in 1926.
Scientific Applications
Quantum Mechanics
Wave function
Thermodynamics
Stream function
Psychology
Psychology symbol
Mathematics
Digamma function
Fluid Dynamics
Stream function
Symbol Codes
Unicode
Uppercase
- Code: U+03A8
- Hex: Ψ
- Decimal: Ψ
Lowercase
- Code: U+03C8
- Hex: ψ
- Decimal: ψ
HTML
Uppercase
Ψ
HTML entity for uppercase Psi
Lowercase
ψ
HTML entity for lowercase psi
LaTeX
Uppercase
\Psi
LaTeX command for uppercase Psi
Lowercase
\psi
LaTeX command for lowercase psi
Common Usage
Physics
Wave Theory
Wave functions in quantum mechanics
Quantum Mechanics
State vectors and probability amplitudes
Particle Physics
Particle wave functions
Engineering
Fluid Mechanics
Stream functions
Heat Transfer
Thermal potentials
Acoustics
Sound wave functions
Psychology
Research
Psychological factors
Testing
Mental processes
Analysis
Behavioral patterns
Common Applications
Quantum Mechanics
Schrödinger equation
Expectation value
Wave function expansion
Fluid Dynamics
Velocity components
Vorticity equation
Stream function decomposition
Special Applications
Quantum States
Qubit state
Hydrogen atom
Normalization
Flow Analysis
Couette flow
Potential flow
Streamlines
Quantum Mechanical Applications
Wave Functions
- • Particle in a box
- • Harmonic oscillator
- • Hydrogen atom
- • Quantum tunneling
Quantum States
- • Superposition states
- • Entangled states
- • Coherent states
- • Mixed states
Measurements
- • Observable operators
- • Expectation values
- • Probability densities
- • Collapse of wave function
Theoretical Applications
Mathematical Physics
Digamma function
Polygamma function
Euler-Mascheroni constant
Quantum Field Theory
Dirac Lagrangian
Field expansion
Propagator
Wave Equations
Time-Dependent
Schrödinger equation
General solution
Probability density
Time-Independent
1D stationary states
Particle in a box
Energy levels
Writing Guidelines
Uppercase and lowercase both have a trident shape with different proportions (Ψ, ψ). In handwriting, ensure the three prongs are clearly visible and the stem is straight. The lowercase ψ should be distinguished from the Greek phi (φ) and the Latin w.
How to Type Psi
Windows
Alt Code
- Hold Alt
- Type 936 for Ψ or 968 for ψ
- Release Alt
Character Map
- Open Character Map
- Select Greek
- Find and copy Psi
Unicode
- Hold Alt + X
- Type 03A8 for Ψ or 03C8 for ψ
- Release Alt + X
macOS
Option Key
- Press Option + y for ψ
Character Viewer
- Press Control + Command + Space
- Select Greek
- Click Psi
Linux
Compose Key
- Press Compose + p + s for ψ
Unicode
- Press Ctrl + Shift + U
- Type 03C8
- Press Enter
Frequently Asked Questions
Why is psi used for wave functions?
Ψ was chosen by Erwin Schrödinger in 1926 to represent quantum mechanical wave functions. The choice was arbitrary but has become standard notation in quantum mechanics.
What's the difference between Ψ and ψ in quantum mechanics?
Uppercase Ψ typically represents the total wave function of a system, while lowercase ψ often represents individual wave functions or components. However, this convention isn't strictly followed in all texts.
How is psi used in psychology?
In psychology, ψ (psi) is used as a general symbol for psychological phenomena and mental processes. It's also associated with parapsychology research, though this is a distinct field from mainstream psychology.
What's the difference between ψ and φ?
While both letters are used in quantum mechanics, ψ (psi) typically represents wave functions, while φ (phi) often represents phase angles or scalar fields. They have distinct shapes: ψ has three prongs, while φ has a loop.