The initials PDE can stand for:
- Page Directory Entry, a list of page table addresses in computer science
- Partial differential equation, a differential equation involving partial derivatives of a function of several variables
- European Democratic Party (EDP), in Spanish, French and Italian
- Phosphodiesterase, a kind of enzyme important in intracellular communication
- "Parade" on street signs
- Photon detection efficiency
- Eclipse (software), plug-in development environment
- Portable Development Environment, File extension for processing source code
- Position Determining Entity, used by cellular phone companies for location determination
- Position Determining Equipment, used by cellular phone companies for location determination
- Present Day English
- Principle of double effect
- Integrated Development Environment, (program development environment) an editing and debugging tool used during software development
- Polydichloric euthimal (sometimes spelled "Polydichloric euthymol"), a fictitious man-made chemical seen in the films Outland, Terminator 2: Judgment Day, and The Relic
- Projectile Development Establishment UK research establishment based at Fort Halstead, and later Aberporth
- Printing Dialog Extensions a user interface for changing printer options in Mac OS X.
- Pug dog encephalitis
- Pulse Detonation Engine a proposed substitute to the traditional jet engine.