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Japan 
MENA 
- MTI
- MTR
- MTS
- MTT assay
- MTTR
- MTU
- MUC
- MUC1
- MUD
- MVA
- MVC
- MVK
- MVP
- MVTR
- MWD
- MXNet
- MXenes
- MYB
- Maars
- Mac
- Mac Pro
- MacConkey agar
- MacCormack method
- MacPherson strut
- Macadam
- Mace
- Maceration
- Macf1
- Mach number
- Mach's principle
- Machinability
- Machine
- Machine age
- Machine code
- Machine elements
- Machine epsilon
- Machine ethics
- Machine guarding
- Machine industry
- Machine learning
- Machine olfaction
- Machine perception
- Machine press
- Machine shop
- Machine tending
- Machine to machine
- Machine tool builder
- Machine tools
- Machine translation
- Machine vision
- Machine-generated data
- Machine-readable
- Machine-readable passport
- Machining
- Machining vibrations
- Machinists
- Macintosh
- Mackinawite
- Macrocell
- Macrocycles
- Macrocyclic
- Macrocyclic ligand
- Macroemulsion
- Macroglobulinemia
- Macrograph
- Macrolides
- Macromolecular crowding
- Macromolecules
- Macromonomers
- Macrophage colony-stimulating factor
- Macrophage polarization
- Macrophages
- Macropores
- Macros
- Macroscopic
- Macroscopic scale
- Macroscopic traffic flow model
- Macrosomia
- Macrovascular disease
- Macula densa
- Macular
- Macular degeneration
- Macular edema
- Macular hole
- Maculopapular rash
- Maculopathy
- Madelung constant
- Madin-Darby canine kidney cells
- Maf
- Mafic
- Magainin
- Magdeburg hemispheres
- Maghemite
- Magic angle
- Magic bullets
- Magic constant
- Magic squares
- Magic tee
- MagicDraw
- Maglev