| Acronym | Meaning |
| PCU | Process Control Unit |
| PCV | Positive Crankcase Ventilation |
| PD | Photoelectron Diffraction |
| PDA | Phase Doppler Analysis |
| PDA | Photodiode Array |
| PDAP | Poly(diallyl Phthalate) |
| PDB | Peedee Belemnite |
| PDB | Protein Data Bank |
| PDB | Potato Dextrose Broth |
| PDCAAS | Protein Digestibility Correlated Amino Acid Score |
| PDDO | Projection Of Diatomic Differential Overlap |
| PDE | Partial Differential Equation |
| PDEA | Preliminary Draft Environmental Assessment |
| PDECD | Pulsed Discharge Electron Capture Detector |
| PDEIS | Preliminary Draft Environmental Impact Statement |
| PDES | Preliminary Draft Environmental Statement |
| PDF | Powder Diffraction File |
| PDF | Pair Distribution Function |
| PDF | Planar Deformation Feature |
| PDF | Probability Density Function |
| PDF | Probability-distribution Function |
| PDFT | Perturbation Density-functional Theory |
| PDG | Patent Documentation Group |
| PDGF | Platelet-derived Growth Factor |
| PDGFR | Platelet-derived Growth Factor Receptor |
| PDI | Point Dipole Interaction (model For Mol.-polarizability Calcns.) |
| PDI | Polarization-division Interferometry |
| PDI | Polydispersity Index |
| PDK | Pyruvate Dehydrogenase Kinase |
| PDLC | Polymer-dispersed Liquid Crystal |
| PDM3.1 | Probabilistic Dilution Model Version 3.1 |
| PDMEE | Primary-beam Diffraction Modulated Electron Emission |
| PDMS | Plasma Desorption Mass Spectrometry |
| PDP | Plasma Display Panel |
| PDPA | Phase Doppler Particle Analyzer |
| PDPID | Pulsed Discharge Photoionization Detector |
| PDQ | Physician Data Query |
| PDR | Photodissociation Region |
| PDR | Photon-dominated Region |
| PDR | Proliferative Diabetic Retinopathy |
| PDRM | Post-depositional Remanent Magnetization |
| PDS | Photothermal Deflection Spectroscopy |
| PDS | Piecewise Direct Standardization |
| PDSA | Peroxydisulfuric Acid |
| PDT | Photodynamic Therapy |
| PDU | Process Development Unit |
| PDVB | Poly(divinyl Benzene) |
| PDVSA | Petroleos De Venezuela |
| PE | Performance Evaluation |
| PE | Population Equivalent (in Wastewater Treatment) |