PI

PI may refer to:

Arts and media

 * Politically Incorrect (blog), a German political blog
 * Seattle Post-Intelligencer or P-I, a newspaper in the United States
 * Primitive Instinct, an English rock band formed in 1987
 * P.I. (TV series), 2017 Singaporean TV series

Political parties

 * Partido Independiente or Independent Party, a political party in Uruguay
 * Partido Intransigente or Intransigent Party, an Argentine political party
 * Partit per la Independència, a political party in Catalonia (Spain) of the 1990s

Other businesses and organizations

 * Perimeter Institute for Theoretical Physics, a research centre in Ontario, Canada
 * Privacy International, a UK-based charity that supports the right to privacy across the world
 * Defunct Piedmont Airlines (1948–89) (IATA airline code PI)
 * Philadelphia International, record label founded in 1971

Biology and medicine

 * Parental investment, in evolutionary biology
 * Paternity Index, a value used to calculate probability of paternity
 * Pistillata, a gene that influences the development of flowers in the ABC model of flower development
 * Phosphatidylinositol, a class of lipids
 * Ponderal index, a measure of leanness of a person (similar to body mass index)
 * Propidium iodide, a chemical used as a DNA stain
 * Primary immunodeficiency
 * Protease inhibitor (pharmacology), class of drugs used to treat or prevent infection by viruses, including HIV and Hepatitis C
 * Protease inhibitor (biology), molecules that inhibit the function of proteases
 * Pulsatility index, a ratio of blood flow rates

Computing

 * Persistent identifier, a long-lasting reference to a digital object
 * Processing Instruction, an SGML and XML node type
 * Programmed instruction, a technology invented to improve teaching
 * Provider-independent address space, a type of internet (IP) address

Other uses in science and technology

 * Isoelectric point (pI), the pH at which a particular molecule or surface carries no net electrical charge.
 * Power integrity, in digital electronics
 * PI controller, a concept in automation and control engineering
 * Plasticity index, a measure of the plasticity of a soil
 * Polyimide, a polymer of imide monomers
 * Preußische Instruktionen, a cataloging system for libraries
 * Principal investigator, the lead scientist or engineer for a particular project

Other uses

 * Pass interference, a foul in American and Canadian gridiron football
 * People's Initiative, one of the modes in which the constitution of the Philippines could be amended
 * Philippine Islands (P. I.), the commonly used name of the Philippines during the US colonial period
 * Pirot, a city located in south-eastern Serbia (license plate code PI)
 * Political incorrectness or politically incorrect, commonly abbreviated to PI or PIC
 * Pro forma invoice, in business
 * Private investigator (P.I.), a person who can be hired to undertake investigations
 * Profitability index, the ratio of payoff to investment of a proposed project
 * Personal injury