Psi, PSI or Ψ may refer to:
Alphabetic letters
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Psi (Greek) (Ψ or ψ), the twenty-third letter of the Greek alphabet
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Psi (Cyrillic), letter of the early Cyrillic alphabet, adopted from Greek
Arts and entertainment
Comics
Music
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PSI (album), album by Pitchshifter (2002)
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Psi Com, 1980s rock band
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Psi Power, song by rock group Hawkwind (1978)
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Psi Records, music record label
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PSI Records, music record label
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Ψ CMX DVD, Finnish language video album by the band CMX
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Pitch Shifter Industries, acronym used by the British band Pitchshifter
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Logo used by the band Twenty One Pilots during their Scaled and Icy (2021) album era
Other uses in arts and entertainment
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Psi (TV series), Brazil
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Psi Corps, in the Babylon 5 fictional universe
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, Canadian television series
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, 2004 video game
Organizations
Government and politics
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Italian Socialist Party ( Partito Socialista Italiano), socialist and later social-democratic political party in Italy
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Italian Socialist Party (2007), social-democratic political party in Italy
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Indonesian Solidarity Party ( Partai Solidaritas Indonesia)
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Indonesian Socialist Party ( Partai Sosialis Indonesia)
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Proliferation Security Initiative, against weapons technology transfer
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Public Sector Information, as in:
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The 2003 EU Directive on the re-use of public sector information
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The UK Office of Public Sector Information (OPSI), formerly HMSO
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United States Senate Homeland Security Permanent Subcommittee on Investigations
Other organizations
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Paul Scherrer Institute, research institute in Villigen, Switzerland
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Pechersk School International, Kyiv, Ukraine
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Physics Society of Iran
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Planetary Science Institute, Tucson, Arizona, US
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Poetry Slam, Inc., promoting poetry
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Policy Studies Institute, UK research organization
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Population Services International, global health organization
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Professional Skills Institute, technical school in Maumee, Ohio, US
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Prudential Securities Incorporated, financial services company
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PSI Seminars, on awareness training
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Public Services International, trades unions federation
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Statisticians in the Pharmaceutical Industry
Parapsychology
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Psi (parapsychology), psychic or paranormal phenomena
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Psi hit, parapsychological experimentation term
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Paranormal Site Investigators, in the UK
Science, technology, and mathematics
Biology and medicine
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PSI (prion), infectious protein in yeast
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Pandemic severity index, former US CDC influenza scale
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Photosystem I, protein complex involved in photosynthesis
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Pneumonia severity index
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Protein Structure Initiative, of the U.S. NIGMS
Computing
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Psi (instant messaging client), XMPP client program
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Potentially Shippable Increment, in the Scrum software development methodology
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Program-specific information, part of the MPEG transport stream protocol
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Pressure stall information, a Linux kernel patch for out of memory management
Cryptography
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Private set intersection, a cryptographic technique to compute the intersection of two encrypted sets
Economics
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PSI-20, Lisbon, Portugal stock market index
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Private sector involvement, in sovereign debt crisis resolution
Engineering
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"Yaw" angle, one of the Euler angles, denoted ψ in aerospace engineering
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Present serviceability index, a pavement performance indicator introduced by AASHTO
Geography
Mathematics
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Chebyshev function
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Dedekind psi function
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Digamma function
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Polygamma functions
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Stream function, in two-dimensional flows
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Polar tangential angle of a curve
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Probability of ultimate ruin, in ruin theory
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Supergolden ratio
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Reciprocal Fibonacci constant
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Population Stability Index (Kullback–Leibler divergence#Symmetrised divergence)
Physics and chemistry
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Pound per square inch, unit of pressure
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PSI (computational chemistry), software
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J/psi meson, subatomic particle
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Porous silicon ("PS" or "pSi"), a form of silicon with introduced nanopores in its microstructure
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Water potential, denoted Ψ, in physical chemistry, the potential energy of a water solution relative to pure water
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Wave function, denoted ψ, in quantum mechanics
Psychology
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Psychology or psychologist, denoted Ψ, used in the logo of various psychological associations
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Psi Chi, the National Honor Society in psychology
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Psi-theory, theory about the human mind, a cognitive architecture
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Psychiatric Solutions, Inc., corporation that owns psychiatric hospitals
Other uses
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Parasocial interaction, non-reciprocal interactions, as between a fanbase and a performer
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Permanent staff instructor, in the British Army
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Personalized System of Instruction
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Pollutant Standards Index, air pollution measure
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Pre-shipment inspection, method of quality control
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Presentence investigation report, investigation into the history of person convicted of a crime
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Proto-Siouan language, the reconstructed ancestor of the Siouan languages
See also
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Psy (disambiguation)
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PS1 (disambiguation)
