| Acronym | Meaning |
 | POY | Partially Oriented Yarn (usually Synthetics |
| PP | Pariser Parr |
| PP | Polarization Propagator |
| PP-MRD-CI | Pseudopotential-multireference Double Excitation-CI |
| PPA | Pollution Prevention Act (of 1990) |
| PPAC | Parallel-plate Avalanche Counter |
| PPAD | Parallel-plate Avalanche Detector |
| PPAR | Peroxisome Proliferator-activated Receptor |
| PPB | Parts Per Billion |
| PPBA | Plane-wave Plane-wave Born Approximation |
| PPC | Polypropylene Carbonate |
| PPCP | Pharmaceuticals And Personal Care Products |
| PPD | Purified Protein Derivative |
| PPDS | Physical Property Data Service |
| PPE | Personal Protective Equipment |
| PPE | Poly(phenylene Ether)s |
| PPE | Porcine Pancreatic Elastase |
| PPES | Photopyroelectric Spectroscopy |
| PPFD | Photosynthetic Photon Flux D. |
| PPG | Pike's Peak Granite (USGS Rock Standard) |
| PPG | Polypropylene Glycol |
| PPGA | Plastic Pin Grid Array [electronic Package] |
| PPGVB | Perfect Pairing Generalized Valence Bond (wave Function) |
| PPH | Parts Per Hundred |
| PPHM | Parts Per Hundred Million |
| PPI | Prepulse Inhibition |
| PPI | Proton Pump Inhibitor |
| PPIC | Pollution Prevention Information Clearinghouse |
| PPKTP | Periodically Poled KTiOPO4 |
| PPLN | Periodically Poled Lithium Niobate |
| PPLO | Pleuropneumonia-like Organism |
| PPLV | Preliminary Pollutant Limit Value |
| PPM | Pair Population Method |
| PPM | Parts Per Million |
| PPM | Path Probability Method |
| PPMA | Parts Per Million Atomic |
| PPMSVX | Pseudopotential Multiple-scattering Valence-exchange |
| PPN | Peroxypropionyl Nitrate |
| PPO | Poly (phenylene Oxide) |
| PPP | Positron Polarization Potential |
| PPPA | Poison Prevention Packaging Act |
| PPQ | Parts Per Quadrillion |
| PPR | Projection Pursuit Regression |
| PPS | Poly (phenylene Sulfide) |
| PPT | Parts Per Trillion |
| PPT-MCF | Pseudo-polarization Tensor-mutually Consistent Field ( For Mol. Interactions) |
| PPV | Poly(p-phenylene Vinylene) |
| PPV | Poly(phenylene Vinylene) |
| PQC | Piezoelectric Quartz Crystal |
| PQCD | Perturbative Quantum Chromodynamics |
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