- Mole fraction
- Molecular diffusion
- Molecular distillation
- Molecular dynamics
- Molecular geometry
- Molecular mass
- Molecular motors
- Molecular orbital
- Molecular orbital theory
- Molecular sieves
- Molecular symmetry
- Molecular vibration
- Molecule-based magnets
- Molten salt
- Molten-salt reactor experiment
- Molybdate
- Molybdenum
- Molybdenum disilicide
- Molybdenum disulfide
- Moment
- Moment distribution method
- Moment magnitude scale
- Momentum
- Monatomic gases
- Monazite
- Monel
- Monocalcium phosphate
- Monochloramine
- Monoclinic crystal system
- Monocoque
- Monocrystalline silicon
- Monohydrocalcite
- Monomers
- Monorail
- Monosaccharides
- Monosodium glutamate
- Monotonic function
- Monsoon
- Montmorillonite
- Monzogranite
- Monzonite
- Moore's Law
- Moraines
- Mordant
- Morphology
- Morse code
- Mortar
- Mother liquor
- Motherboard
- Motor oil
- Motor vehicle
- Moving load
- Moving parts
- Mu-metal
- Mucociliary clearance
- Mucous membranes
- Mucus
- Mud
- Mud cake
- Mud pump
- Mudbrick
- Mudrock
- Mudstone
- Muffler
- Mulch
- Mullite
- Multi-junction solar cells
- Multi-stage flash distillation
- Multicellular organisms
- Multipath propagation
- Multiplication
- Multiplicative inverse
- Multipole expansion
- Municipal solid waste
- Muscle
- Muscle cells
- Muscle contraction
- Muscovite
- Mutagens
- Muzzle blast
- Muzzle velocity
- Mycobacterium smegmatis
- Mycotoxins
- Myelin
- Myocardial infarction
- Myocarditis
- Myoglobin
- NAT
- NBO
- NMR
- NORM
- NOx
- NPV
- NSF
- Nacelles
- Nadcap
- Nahcolite
- Nanoclusters
- Nanocomposites
- Nanoconcrete
- Nanocrystals
- Nanofibers
- Nanoflower
- Nanofluid
- Nanoindentation
- Nanomaterials
- Nanometre
- Nanoparticles
- Nanorods
- Nanoseconds
- Nanostructures
- Nanotechnology
- Nanotextured surfaces
- Nanowires
- Naphtha
- Naphthalene
- Nasal spray
- Nasolacrimal duct
- National Grid
- Nationally determined contribution
- Native copper
- Native metals
- Natron
- Natural abundance
- Natural building
- Natural dyes
- Natural fibers
- Natural frequency
- Natural gas processing
- Natural products
- Natural resource
- Natural rubber
- Natural uranium
- Nausea
- Navier-Stokes equations
- Navigability
- Near-infrared spectroscopy
- Necking
- Necrosis
- Negative feedback
- Negative temperature
- Negative thermal expansion
- Neodymium
- Neodymium magnets
- Neon
- Neon signs
- Neopentane
- Neoprene
- Nepheline syenite
- Nephrons