Psi (letter)

Psi (Ψ ψ) is the 23rd letter of the Greek alphabet and has a numeric value of 700.

Related Topics:
Greek alphabet - Numeric

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It is also used as a symbol/icon for psychology.

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It is perhaps most famous in science for representing a wavefunction in quantum mechanics, particularly with the Schrödinger equation.

Related Topics:
Wavefunction - Quantum mechanics - Schrödinger equation

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Psi is also used as the symbol for the polygamma function, defined by

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: psi_n(x) = rac{d^{(n)}}{dx^{(n)}}rac{Gamma '(x)}{Gamma (x)},!

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where Gamma (x) is the gamma function.

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