Psi
| Greek letters | |
| Α α Alpha | Β β Beta |
| Γ γ Gamma | Δ δ Delta |
| Ε ε Epsilon | Ϝ ϝ Digamma |
| Ζ ζ Zeta | Η η Eta |
| Θ θ Theta | Ι ι Iota |
| Κ κ Kappa | Λ λ Lambda |
| Μ μ Mu | Ν ν Nu |
| Ξ ξ Xi | Ο ο Omicron |
| Π π Pi | Ϻ ϻ San |
| Ϙ ϙ Qoppa | Ρ ρ Rho |
| Σ σ Sigma | Τ τ Tau |
| Υ υ Upsilon | Φ φ Phi |
| Χ χ Chi | Ψ ψ Psi |
| Ω ω Omega | Ϡ ϡ Sampi |
| Greek alphabet | |
Psi (Ψ ψ) is the 23rd letter of the Greek alphabet and has a numeric value of 700.
It has come to be a symbol for psychology-related topics, and has also been used as a shorthand for supposed psychic abilities or powers.
See also PSI (pounds per square inch).
Psi was also a character on the formerly popular game and television series, PokÃÂémon.
The lower-case letter ψ is used as the symbol for the wave function in quantum mechanics.
Psi is also an open-source instant messenger. See Psi (software).