PI

• 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

• {{lang|es|Partido Independiente}} or Independent Party, a political party in Uruguay
• {{lang|es|Partido Intransigente}} or Intransigent Party, an Argentine political party
• Partit per la Independència, a political party in Catalonia (Spain) of the 1990s

• 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

• 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

• 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

• 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
• {{lang|de|Preußische Instruktionen}}, a cataloging system for libraries
• Principal investigator, the lead scientist or engineer for a particular project

• 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
• Personal injury
• 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
• Preliminary injunction, an injunction issued by a court prior to a final determination of the merits of a legal case
• Private investigator, a person who can be hired to undertake investigations
• Pro forma invoice, in business
• Profitability index, the ratio of payoff to investment of a proposed project

{{canned search|PI|P-I}}

• Pi (disambiguation)
• P1 (disambiguation)
• PL (disambiguation)
• {{intitle|P-I}}
• {{srt|1}}

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