PID

Medicine

Pelvic inflammatory disease or pelvic inflammatory disorder, an infection of the upper part of the female reproductive system
Primary immune deficiency, disorders in which part of the body's immune system is missing or does not function properly
Prolapsed intervertebral disc, commonly called a herniated disc

BBC Programme Identifier, a unique identifier for a BBC television or radio programme brand, a season or series, or an individual episode
OBD-II PIDs (on-board diagnostics parameter IDs), requests for data through an OBD connector in automotive repair
Packet Identifier, a field in a MPEG transport stream packet
Partial information decomposition, an extension of information theory
Passive infrared detector, a passive infrared sensor
Payload Interface Document (used on space engineering program for example)
Persistent identifier, a long-lasting reference to a document, file, web page, or other object
Phosphotyrosine-interacting domain, also known as phosphotyrosine-binding domain, a protein domain which bind to phosphotyrosine
Photoionization detector, measures volatile organic compounds and other gases
Physical Interface Device, a class of a USB device
PID controller (proportional-integral-derivative controller), a control concept used in automation
Piping and instrumentation diagram (P&ID), a diagram in the process industry which shows the piping of the process flow etc.
Principal ideal domain, an algebraic structure
Process identifier, a number used by many operating systems to identify a process

Police Intelligence Department, a staff department of the Singapore Police Force
Political Intelligence Department (disambiguation), multiple organisations
Politieke Inlichtingen Dienst (Political Intelligence Department), was the main security agency for the Dutch East Indies
Prague Integrated Transport (Pražská integrovaná doprava – PID in Czech), an integrated public transport system in Prague

Pathways into Darkness, a 1993 video game by Bungie
"Paul is dead", a 1960s urban legend that Paul McCartney was dead
Pid (video game), a 2012 video game by Might and Delight
Project Initiation Documentation, in project management
Party identification, the political party with which an individual identifies
Everett Pid Purdy (1904–1951), American athlete who played in both Major League Baseball and the National Football League