Psi has multiple meanings:

• Psi (letter) (Ψ, ψ) of the Greek alphabet
• Psi (Cyrillic) (Ѱ, ѱ), letter of the early Cyrillic alphabet, adopted from Greek
• Psi (parapsychology)
• Psi (instant messaging client), a popular Jabber client program
• J/ψ particle, a subatomic particle
• Wavefunction in Quantum Mechanics, ψ
• In mathematics, Ψ is used to denote the angle between the tangent and the x-axis in the intrinsic coordinates system
• Again in mathematics, Ψ is also used to denote the Digamma and Polygamma functions.
• PSI (prion), an infectious protein in yeast
• Psi, is a common shortening of the word psychic
• Psi (comics), a DC Comics character
• An abbreviation of the Psion (Dungeons & Dragons) or Psionicist character class

A homophone of Psi is Sai, which is an Asian weapon shaped (probably coincidentally) like the Greek letter Psi. Look up Ψ, ψ in Wiktionary, the free dictionary. ... Psi (Ѱ, ѱ) is a letter in the early Cyrillic alphabet, derived from the Greek letter psi (Ψ, ψ). It represents the sound /ps/, as in English naps, and was used largely in loan words from foreign languages. ... In parapsychology, psi is defined as the active agent by which mind influences matter and is able to receive ESP impressions. ... Psi is a GPLed instant messaging client for the Jabber (XMPP) protocol which uses the Qt toolkit. ... The title given to this article is incorrect due to technical limitations. ... This article discusses the concept of a wavefunction as it relates to quantum mechanics. ... Fig. ... Important points in intrinsic coordinates Intrinsic coordinates is a coordinate system which defines points upon a curve partly by the nature of the tangents to the curve at that point. ... In mathematics, the digamma function is defined as the logarithmic derivative of the gamma function: It is the first of the polygamma functions. ... In mathematics, the polygamma function of order m is defined as the m+1 th derivative of the logarithm of the gamma function: Here is the digamma function and is the gamma function. ... It has been suggested that this article or section be merged with Fungal prions. ... The term psychic comes from the Greek psychikos, meaning of the soul, mental, which is in turn derived from the Greek word psyche (soul/mind). ... Psi is a DC character created by Paul Kupperberg and Carmine Infantino for Daring New Adventures of Supergirl #1 (November 1982). ... DC Comics is one of the largest American companies in comic book and related media publishing. ... In the Dungeons & Dragons role-playing game, psion or psionicist is one of the optional character classes. ... In the Dungeons & Dragons fantasy role-playing game, the psionicist is a character class that utilizes psionic powers. ... Look up Homophone in Wiktionary, the free dictionary. ... Two sai For other meanings of the word sai, see Sai (disambiguation). ...

PSI stands for:

• Pandemic Severity Index
• pound-force per square inch (psi), a non-SI unit of pressure
• PSI (computational chemistry) software
• Pandemic Severity Index by Centers for Disease Control and Prevention
• Italian Socialist Party (Partito Socialista Italiano)
• Paul Scherrer Institute in Villigen, Switzerland
• Permanent Staff Instructor in the British Army
• Permanent Subcommittee on Investigations (PSI) of the U.S. Senate
• Pollutant Standards Index, an air pollution index developed by the United States Environmental Protection Agency (USEPA)
• Population Services International, an international healthcare NGO based in Washington D.C.
• Professional Secretaries International
• Presentence Investigation
• Professors for a Strong Israel
• Program Specific Information, metadata for digital transmission
• Proliferation Security Initiative
• Project Server Interface, programming interface for MS-Project servers
• Public Services International, a global union federation of public sector trade unions
• Socialist Party of the Islands (Partit Socialista de les Illes)
• People with Speech Impairment
• Pechersk School International, a school in Kiev
• Protein Synthesis Inhibition
• Printing Souvenirs Inclusive, a Chicago souvenirs distributor
• Postpartum Support International, 501(c)3 organization devoted to women's mental health issues
• Statisticians In The Pharmaceutical Industry, the PSI acronym (rather than SPI) is chosen for its relation to the Greek letter Ψ, commonly used in statistical formulae.
• Personal Soldier Inc., an Arizona based bodyguard firm (www.personalsoldier.com)

pSi stands for: The Pandemic Severity Index (PSI) is a scale or index created in January 2007 by the United States Centers for Disease Control and Prevention (CDC) designed to mimic the system for indexing the severity of hurricanes (which is the Saffir-Simpson Hurricane Scale for tropical cyclones). ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in2) is a non-SI unit of pressure based on avoirdupois units. ... PSI is a computational chemistry package originally written by the research group of H. F. Schaefer III. Primary development of PSI3 has been carried out by Daniel Crawford, David Sherrill, Edward Valeev, and Rollin King. ... The Pandemic Severity Index (PSI) is a scale or index created in January 2007 by the United States Centers for Disease Control and Prevention (CDC) designed to mimic the system for indexing the severity of hurricanes (which is the Saffir-Simpson Hurricane Scale for tropical cyclones). ... The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, is recognized as the leading United States agency for protecting the public health and safety of people. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The Paul Scherrer Institute (PSI) is an multi-disciplinary research institute. ... A Permanent Staff Instructor is a senior member of the full time British Army, selected to teach the Reserve and Territorial Army soldiers. ... The Permanent Subcommittee on Investigations (PSI) of the U.S. Senate Committee on Homeland Security and Governmental Affairs is currently chaired by Senator Norm Coleman (R-MN), with Carl Levin (D-MI) as a ranking member. ... The Pollutant Standards Index, or PSI, provides a uniform system of measuring pollution levels for the major air pollutants. ... EPA redirects here. ... Population Services International (PSI): PSI is a nonprofit organization based in Washington, D.C. that harnesses the vitality of the private sector to address the health problems of low-income and vulnerable populations in 70 developing countries. ... The International Association of Administrative Professionals (IAAP) was formed in Kansas City, Missouri in 1942. ... A presentence investigation report (PSI) is a legal term referring to the investigation into the history of person convicted of a crime before sentencing to determine if there are extenuating circumstances which should ameliorate the sentence or a history of criminal behavior to increase the harshness of the sentence. ... Professors for a Strong Israel is a far-right organization of academics united by a shared concern for the security and the Jewish character of the State of Israel, and support the principle of Greater Israel. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The Proliferation Security Initiative (PSI) is an international effort led by the United States to interdict transfer of banned weapons and weapons technology. ... Public Services International (PSI) is a global union federation of public sector trade unions. ... PSI sticker Socialist Party of the Islands (in Catalan: Partit Socialista de les Illes) was a political party in the Balearic Islands, Spain. ... Postpartum Support International (PSI) is an international 501(c)(3) non-profit devoted to eliminating the denial and ignorance of emotional health related to childbirth. ... Statisticians in the Pharmaceutical Industry, abbreviated to PSI, is an organisation for the promotion of statistical thinking in order to improve the quality of research and development in the pharmaceutical industry. ...

• Porous silicon
• protective security international, a british security company

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