Editing Psi

{{wiktionary|PSI|Psi|psi}}
'''Psi''', '''PSI''' or '''Ψ''' may refer to:
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==Alphabetic letters==
* [[Psi (Greek)]] (Ψ or ψ), the twenty-third letter of the Greek alphabet
* [[Psi (Cyrillic)]], letter of the early Cyrillic alphabet, adopted from Greek

==Arts and entertainment==
* "Psi" as an abbreviation for [[psionics]]

===Comics===
* [[Psi (comics)]], DC Comics character
* Psi Division, division in the ''[[Judge Dredd]]'' and ''2000 AD'' series of comics
* ''[[Psi-Force]]'', comic series
* [[Psi-Hawk]], comic character
* ''[[Psi Lords]]'', comic series

===Music===
* [[PSI (album)|''PSI'' (album)]], album by Pitchshifter (2002)
* [[Psi Com]], 1980s rock band
* [[Psi Power]],  song by rock group Hawkwind (1978)
* [[Psi Records]], music record label
* [[PSI Records]], music record label
* Ψ [[CMX DVD]], Finnish language video album by the band CMX
* ''Pitch Shifter Industries'', acronym used by the British band [[Pitchshifter]]
* Logo used by the band [[Twenty One Pilots]] during their ''[[Scaled and Icy]]'' (2021) album era

===Other uses in arts and entertainment===
* [[Psi (TV series)|''Psi'' (TV series)]], Brazil
* [[Psi Corps]], in the ''Babylon 5'' fictional universe
* ''[[Psi Factor: Chronicles of the Paranormal]]'', Canadian television series
* ''[[Psi-Ops: The Mindgate Conspiracy]]'', 2004 video game

==Organizations==

===Government and politics===
* [[Italian Socialist Party]] (''Partito Socialista Italiano''), socialist and later social-democratic political party in Italy
* [[Italian Socialist Party (2007)]], social-democratic political party in Italy
* [[Indonesian Solidarity Party]] (''Partai Solidaritas Indonesia'')
* [[Indonesian Socialist Party]] (''Partai Sosialis Indonesia'')
* [[Proliferation Security Initiative]], against weapons technology transfer
* ''Public Sector Information'', as in:
** The 2003 EU [[Directive on the re-use of public sector information]]
** The UK [[Office of Public Sector Information]] (OPSI), formerly HMSO
* [[United States Senate Homeland Security Permanent Subcommittee on Investigations]]

===Other organizations===
* [[Paul Scherrer Institute]], research institute in Villigen, Switzerland
* [[Pechersk School International]], Kyiv, Ukraine
* [[Physics Society of Iran]]
* [[Planetary Science Institute]], Tucson, Arizona, US
* [[Poetry Slam, Inc.]], promoting poetry
* [[Policy Studies Institute]], UK research organization
* [[Population Services International]], global health organization
* [[Professional Skills Institute]], technical school in Maumee, Ohio, US
* [[Prudential Securities Incorporated]], financial services company
* [[PSI Seminars]], on awareness training
* [[Public Services International]], trades unions federation
* [[Statisticians in the Pharmaceutical Industry]]

== Parapsychology ==
{{For|mainstream psychology|#Psychology}}
* [[Psi (parapsychology)]], psychic or paranormal phenomena
* [[Psi hit]], parapsychological experimentation term
* [[Paranormal Site Investigators]], in the UK

==Science, technology, and mathematics==

===Biology and medicine===
{{for|psychology|#Psychology}}
* [[PSI (prion)]], infectious protein in yeast
* [[Pandemic severity index]], former US CDC influenza scale
* [[Photosystem I]], protein complex involved in photosynthesis
* [[Pneumonia severity index]]
* [[Protein Structure Initiative]], of the U.S. NIGMS

===Computing===
* [[Psi (instant messaging client)]], XMPP client program
* [[Potentially Shippable Increment]], in the Scrum software development methodology
* [[Program-specific information]], part of the MPEG transport stream protocol
* Pressure stall information, a Linux kernel patch for [[out of memory]] management

=== Cryptography ===

* [[Private set intersection]], a cryptographic technique to compute the intersection of two encrypted sets

===Economics===
* [[PSI-20]], Lisbon, Portugal stock market index
* [[Private sector involvement]], in sovereign debt crisis resolution

===Engineering===
* "Yaw" angle, one of the [[Tait-Bryan angles|Euler angles]], denoted ψ in aerospace engineering
*[[Present serviceability index]], a pavement performance indicator introduced by AASHTO

===Geography===
* [[Psi Islands]], in the Melchior Islands, Antarctica
===Mathematics===
* [[Chebyshev function]]
* [[Dedekind psi function]]
* [[Digamma function]]
* [[Polygamma function]]s
* [[Stream function]], in two-dimensional flows
* [[Tangential angle#Polar|Polar tangential angle]] of a curve
* Probability of ultimate ruin, in [[ruin theory]]
* [[Supergolden ratio]]
*[[Reciprocal Fibonacci constant]]
* Population Stability Index ([[Kullback–Leibler divergence#Symmetrised divergence]])

===Physics and chemistry===
* [[Pound per square inch]], unit of pressure
* [[PSI (computational chemistry)]], software
* [[J/psi meson]], subatomic particle
* [[Porous silicon]] ("PS" or "pSi"), a form of silicon with introduced nanopores in its microstructure
* [[Water potential]], denoted Ψ, in physical chemistry, the potential energy of a water solution relative to pure water
* [[Wave function]], denoted ψ, in quantum mechanics

===Psychology===
{{for|paranormal phenomena|#Parapsychology}}
* [[Psychology]] or psychologist, denoted Ψ, used in the logo of various psychological associations
* [[Psi Chi]], the National Honor Society in psychology
* [[Psi-theory]], theory about the human mind, a cognitive architecture
* [[Psychiatric Solutions, Inc.]], corporation that owns psychiatric hospitals

==Other uses==
* [[Parasocial interaction]], non-reciprocal interactions, as between a fanbase and a performer
* [[Permanent staff instructor]], in the British Army
* [[Personalized System of Instruction]]
* [[Pollutant Standards Index]], air pollution measure
* [[Pre-shipment inspection]], method of quality control
* [[Presentence investigation report]], investigation into the history of person convicted of a crime

==See also==
* [[Psy (disambiguation)]]
* [[PS1 (disambiguation)]]

{{disambiguation}}