Medicine

• Prolapsed intervertebral disc
  Spinal disc herniation
  A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine due to trauma, lifting injuries, or idiopathic, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion A spinal disc herniation...
  
  , commonly called a "herniated disc"
• Primary immune deficiency, disorders in which part of the body's immune system is missing or does not function properly
• Pelvic Inflammatory Disease
  Pelvic inflammatory disease
  Pelvic inflammatory disease is a generic term for inflammation of the uterus, fallopian tubes, and/or ovaries as it progresses to scar formation with adhesions to nearby tissues and organs. This may lead to infections. PID is a vague term and can refer to viral, fungal, parasitic, though most...
  
  , (or Pelvic Inflammatory Disorder), an infection and inflammation of the female uterus, fallopian tubes, and/or ovaries

Business

• Project Initiation Document
  Project initiation document
  The Project Initiation Documentation bundles the information which was acquired through the Starting up a Project and Initiating a Project processes in a PRINCE2 controlled project environment...
  
  , all major aspects of the project and forms the basis for its management and the assessment of overall success

Technology

• Photoionization detector
  Photoionization detector
  A photoionization detector or PID is a type of gas detector.Typical photoionization detectors measure volatile organic compounds and other gases in concentrations from sub parts per billion to 10 000 parts per million . The photoionizaton detector is an efficient and inexpensive detector for many...
  
  , measures volatile organic compounds and other gases
• Process identifier
  Process identifier
  In computing, the process identifier is a number used by most operating system kernels to uniquely identify a process...
  
  , a number used by Unix kernels and Windows operating systems to identify a process
• PID controller
  PID controller
  A proportional–integral–derivative controller is a generic control loop feedback mechanism widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a...
  
  , a control concept used in automation. (Proportional/Integral/Derivative)
• Piping and instrumentation diagram
  Piping and instrumentation diagram
  A piping and instrumentation diagram/drawing is a diagram in the process industry which shows the piping of the process flow together with the installed equipment and instrumentation.-Contents and Function:...
  
  , a technical diagram showing all (or a part of) pipelines, instruments, valves, etc., of a process plant
• Process and instrumentation diagram, commonly used in chemical and process engineering
• Passive Infrared Detector, a PIR-based motion detector
• Personal Integrating/Indicating Dosemeter, a type of dosimeter
  Dosimeter
  Dosimeters measure an individual's or an object'sexposure to something in the environment — particularly to a hazard inflicting cumulative impact over long periods of time, or over a lifetime...
  
   for personal use
• Packet Identifier, a field in a MPEG transport stream packet.
• Packet ID, used to identify audio/video streams in DVB "Digital Video Broadcasting"
• Physical Interface Device, a class of USB
  Universal Serial Bus
  USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
  
   devices.

Organizations

• Police Intelligence Department
  Police Intelligence Department
  The Police Intelligence Department is a staff department of the Singapore Police Force. Its primary purpose is to collate and analyse information obtained from the various departments of the SPF, as well as other sources, to support law enforcement activities in Singapore...
  
  , a staff department of the Singapore Police Force
• Political Intelligence Department
  Political Intelligence Department
  The Political Intelligence Department was a department of the British Foreign Office during World War II. Established in 1939, its main function was the production of weekly intelligence summaries...
  
  , a British clandestine body created to produce and disseminate propaganda during WWII.

Other

• Pathways Into Darkness
  Pathways Into Darkness
  Pathways into Darkness is a first-person adventure video game developed and published by Bungie Software Products Corporation in 1993, exclusively for Apple Macintosh personal computers. Players assume the role of a Special Forces soldier who must stop a powerful, godlike being from awakening and...
  
  , a 1993 video game by Bungie Studios
• Parameter ID
  OBD-II PIDs
  OBD-II PIDs are codes used to request data from a vehicle, used as a diagnostic tool. SAE standard J/1979 defines many PIDs, but manufacturers also define many more PIDs specific to their vehicles...
  
  , in automotive repair, PIDs are requests for data through an OBD connector
• Paul Is Dead
  Paul Is Dead
  "Paul is dead" is an urban legend suggesting that Paul McCartney of the English rock band The Beatles died in 1966 and was secretly replaced by a look-alike....
  
  , a 1960s urban legend that Paul McCartney was dead
• Principal ideal domain
  Principal ideal domain
  In abstract algebra, a principal ideal domain, or PID, is an integral domain in which every ideal is principal, i.e., can be generated by a single element. More generally, a principal ideal ring is a nonzero commutative ring whose ideals are principal, although some authors refer to PIDs as...
  
  , in abstract algebra, an integral domain in which every ideal is principal