Psi

Psi has multiple meanings:

Psi (Ψ ψ) is a letter of the Greek alphabet. See Psi (letter).
The letter Psi was also used in the Early Cyrillic alphabet. See Psi (Cyrillic).
In mathematics (Ѱ, ѱ) is the angle between the tangent and the x-axis in the intrinsic coordinates system.
The lower-case letter ψ is used as the symbol for the wave function in quantum mechanics.
In high-energy physics, Ψ refers to a meson also called the J/Ψ particle
It has come to be a symbol for psychology-related topics, and has also been used as a shorthand for supposed psychic or psionic abilities or powers.
Psi is also an open-source instant messenger. See Psi (instant messenger).
Psi was also a character on the popular game and television series, Pok�mon.

The three-letter abbreviation PSI also stands for

Pounds per square inch (PSI).
The Paul Scherrer Institute in Villigen, Switzerland
The U.S. Senate's Permanent Subcommittee on Investigations
Population Services International in List of Angolan companies
The Italian Socialist Party (Partito Socialista Italiano)

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Psi

See also: Psi, Cyrillic alphabet, Greek alphabet, High-energy physics, Instant messenger, Intrinsic coordinates, Italian Socialist Party, J/Psi particle, List of Angolan companies