| Acronym | Meaning |
| MDHS | Methods For The Determination Of Hazardous Substances |
| MDI | Methylene Di-p-phenylene Isocyanate |
| MDI | Modified Dipole Interaction(model For Mol.-polarizability Calcn.) |
| MDL | Method Detection Level Or Limit |
| MDLC | Multidimensional Liquid Chromatography |
| MDMI | Monodisperse Dried Microparticulate Injector |
| MDO | Max. Degree Of Order |
| MDPE | Medium-density Polyethylene |
| MDQ | Minimum Detectable Quantity |
| MDR | Multidrug Resistance |
| MDS | Matrix-diagonalization Sudden Approximation (for Atom Surface Scattering Calcns.) |
| MDS | Metastable Deexcitation Spectroscopy |
| MDS | Minimum Detectable Signal |
| MDSC | Modulated Differential Scanning Calorimetry |
| MDSRS | Morphology-dependent Stimulated Raman Scattering |
| MDV | Marek's Disease Virus |
| MDW | Mixed Density Wave |
| MDW | Multichannel Distorted Wave (Born Approxn.) |
| MEAN | Multipole-extracted Adiabatic-nuclei (for Electron-molecule Collisions) |
| MEBES | Micro-electron Beam Evaporation Source |
| MEBS | Medium Energy Backscattering Spectrometry |
| MECA | Molecular Emission Cavity Analysis |
| MECA | Multiple Excitation Collisional Activation |
| MECC | Micellar Electrokinetic Capillary Chromatography |
| MECI | Monoexcited Configuration Interaction |
| MECI | Multielectron Configuration Interaction |
| MECOP | Modified Electron Correlation Polarization (potential) |
| MECS | Manufacturing Energy Consumption Survey (DOE) |
| MED | Mean Effective Dose |
| MED | Minimal Erythema Dose |
| MEDLA | Molecular Electron Density Lego Assembler |
| MEDLARS | Medical Literature Analysis And Retrieval System (NLM) |
| MEDO | Multipole Expansion Of Diatomic Overlap Approximation |
| MEDOC | Multipole Expansion Defined (on) One Center (a Wave Function In Calcns. On Atomic And Molecular Collisions) |
| MEE | Migration-enhanced Epitaxy |
| MEECC | Microemulsion Electrokinetic Capillary Chromatography |
| MEED | Medium-energy Electron Diffraction |
| MEEKC | Microemulsion Electrokinetic Chromatography |
| MEF | Mouse Embryonic Fibroblast |
| MEF | Myocyte Enhancer Factor |
| MEG | Mixed Exponentially Generated (wave Function) |
| MEG | Modified Electron Gas (quantum Calcn. Method) |
| MEG4 | Multiexponentially Generated 4 (wave Functions) |
| MEHT | Modified Extended Hueckel Theory |
| MEI | Maximally Exposed Individual |
| MEIA | Microparticle Enzyme Immunoassay |
| MEIS | Medium Energy Ion Scattering |
| MEK | Methyl Ethyl Ketone (butanone) |
| MEKC | Micellar Electrokinetic Chromatography |
| MEKP | Methyl Ethyl Ketone Peroxide |