| Acronym | Meaning |
| SONEX | Subsonic Assessment Ozone And Nitrogen Oxide Experiment |
| SONN | Self-organizing Neural Network |
| SOP | Second-order Potential (method For Positron-atom Scattering) |
| SOP | Split-operator Propagator |
| SOP | Standard Operating Procedure |
| SOP/EA | Split-operator Propagator (for) Electronically Adiabatic (phenomena) |
| SOP/ED | Split-operator Propagator (for) Electronically Diabatic (phenomena) |
| SOPHF | Spin And Orbital Polarized Hartree-Fock |
| SOPHIA | System For Organic Reaction Prediction By Heuristic Approach |
| SOPITA | South Pacific Isotopic And Thermal Anomaly |
| SOPPA | Second-order Polarization Propagator Approxn. |
| SOR | Surface Overflow Rate |
| SORC | Strong Off-resonant Comb |
| SORCE | Solar Radiation And Climate Experiment |
| SORG | Stratospheric Ozone Review Group |
| SORI | Sustained Off-resonance Irradn. |
| SORI-CID | Sustained Off-resonance Irradn. Collision-induced Dissocn. |
| SORP | Southern Oxidants Research Program |
| SOS | Southern Oxidant Study |
| SOS | Surfaces Of Section Method (semiclassical Calcn. Of Eigenvalues) |
| SOTE | Standard Oxygen Transfer Efficiency (of Aeration Diffusers) |
| SOUR | Specific Oxygen Uptake Rate |
| SOW | Statement Of Work |
| SP | Surface Potential |
| SP-RPAE | Spin Polarized-random Phase Approxn. (with) Exchange |
| SPA | Scintillation-proximity Assay |
| SPA | Self-consistent Phonon Approximation |
| SPA | Separated Pair Approxn. (wave Function) |
| SPA | Shielded-potential Approxn. (in Electronic Structure) |
| SPACE | Spatial And Chemical Shift-encoded Excitation |
| SPAD | Single Photon Avalanche Diode |
| SPADA | Simulation Program For Air Dust Concentration Analysis |
| SPADE | Stratospheric Photochemistry |
| SPAES | Spin Polarized Auger Electron Spectroscopy |
| SPAG | Small Particle Aerosol Generator |
| SPALEED | Spot Profile Analysis Low Energy Electron Diffraction |
| SPARC | Scholarly Publishing & Academic Resources Coalition |
| SPARC | Stratospheric Processes And Their Role In Climate |
| SPARC | Secreted Protein Acidic And Rich In Cysteine |
| SPARHEED | Spot Profile Analysis Reflection High-energy Electron Diffraction |
| SPARPES | Spin Polarized Angle-resolved Photoelectron Spectroscopy |
| SPARS | Spatially Resolved Spectroscopy |
| SPASE | South Pole Air Shower Expt. |
| SPB | Strong-potential Born (approxn. For At. Collision Calcns.) |
| SPC | Solid Phase Crystallization |
| SPC | Statistical Process Control |
| SPCC | Spill Prevention Control And Countermeasures |
| SPCC | System Performance Check Compound |
| SPCE | Screen-printed Carbon Electrode |
| SPCE | Surface Plasmon-coupled Emission |