| Acronym | Meaning |
| EMPT | Effective Medium Percolation Theory |
| EMR | Electromagnetic Radiation |
| EMR | Electron Magnetic Resonance |
| EMR | Electronically Mediated Reaction |
| EMS | Electromagnetic Susceptibility |
| EMS | Electron Momentum Spectroscopy |
| EMS | Environmental Management System |
| EMS | Ethyl Methanesulfonate |
| EMSA | Electron Microscopy Society Of America |
| EMSA | Electrophoretic Mobility Shift Assay |
| EMSL | Environmental Monitoring Systems Laboratory |
| EMSL | Environmental Monitoring And Support Laboratory |
| EMT | Effective Mass Theory (in Electronic Wave Functions Calcn.) |
| EMT | Effective-medium Theory (of Bonding In Metallic Systems) |
| EMTB | Effective-medium Tight-binding |
| EMTIC | Emission Measurement Technical Information Center |
| EMTO | Extended Muffin-tin Orbital Method |
| EMTS | Environmental Monitoring Testing Site |
| EMU | Electromagnetic Unit |
| EMUS | Electromagnetic Ultrasonic Testing |
| EMZDO | Exchange Modified Zero Differential Overlap |
| ENA | Energetic Neutral Atoms (astronomical Plasmas) |
| ENAA | Epithermal Neutron Activation Analysis |
| ENAC | Energetic Neutral Atom Camera |
| ENAMAP | Eastern North American Model Of Air Pollution |
| ENAN | Education Native American Network |
| ENC | Effective Nuclear Charge (model For Mol. Property Calcns.) |
| ENCAT | Epoxy Nucleophile Catalyzed Transesterification |
| ENCS | Existing And New Chemical Substances |
| END | Electron Nuclear Dynamics (method In Atomic And Molecular Scattering Calcns.) |
| ENDF | Evaluated Nuclear Data File |
| ENDL | Evaluated Nuclear Data Library |
| ENDOR | Electron Nuclear Double Resonance |
| ENDS | European Nuclear Documentation System |
| ENFET | Enzyme Field-effect Transistor |
| ENIS | Emissive Neutron Imaging And Spectroscopy |
| ENMR | Electrophoretic NMR |
| ENR | Endogenous Nitrate Respiration |
| ENR | Epoxidized Natural Rubber |
| ENSDF | Evaluated Nuclear Structure Data File |
| ENSGTI | Ecole Nationale Superieure En Genie Des Technologies Industrielles |
| ENSO | El Nino Southern Oscillation |
| EO | Equivalent Orbital |
| EO | Ethylene Oxide |
| EOD | Engineering Operations Division |
| EOF | Electroosmotic Flow |
| EOIM | Energetic Oxygen Interaction With Materials |
| EOLM | Electro-optical Light Modulation |
| EOM | Extractable Organic Matter |
| EOM | Equations Of Motion Method (green's Function) |