Psi (Ψ ψ) is the 23rd letter of the Greek alphabet and has a numeric value of 700. It is also used as a symbol/icon for psychology.
It is perhaps most famous in science for representing a wavefunction in quantum mechanics, particularly with the Schrödinger equation.
Psi is also used as the symbol for the polygamma function, defined by
where Γ(x) is the gamma function.
Mycenaean Psi figurines
|Α α Alpha||Β β Beta||Γ γ Gamma|
|Δ δ Delta||Ε ε Epsilon||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||Ρ ρ Rho||Σ σ Sigma|
|Τ τ Tau||Υ υ Upsilon||Φ φ Phi|
|Χ χ Chi||Ψ ψ Psi||Ω ω Omega|
Medieval Greece / Byzantine Empire
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