The mass-to-charge ratio (m/Q) is a physical quantity that is most widely used in the electrodynamics of charged particles.

Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions.

In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time.

Mass is both a property of a physical body and a measure of its resistance to acceleration (rate of change of velocity with respect to time) when a net force is applied. An object's mass also determines the strength of its gravitational attraction to other bodies.

In market rate net metering systems the user's energy use is priced dynamically according to some function of wholesale electric prices.

A spike is a sudden and large price move in the price of an asset—either up or down, but more often used when describing up-moves.

Marine energy or marine power refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences.

The kinetic energy of marine currents can be converted in much the same way that a wind turbine extracts energy from the wind, using various types of open-flow rotors.

The Marangoni effect (also called the Gibbs–Marangoni effect) is the mass transfer along an interface between two fluids due to a gradient of the surface tension.

Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.

Man-made forcings include particle pollution (aerosols) that absorb and reflect incoming sunlight; deforestation, which changes how the surface reflects and absorbs sunlight; and the rising concentration of atmospheric carbon dioxide and other greenhouse gases, which decreases the rate at which heat is radiated to space.

An agreement working towards shared goals that are measured by defined Performance Indicators.

The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential installations.

Magnox is a type of nuclear power/production reactor that was designed to run on natural uranium with graphite as the moderator and carbon dioxide gas as the heat exchange coolant.

It is the form of electrical power that is delivered to homes and businesses through electrical infrastructure in many parts of the world.

The Magnus effect is an observable phenomenon that is commonly associated with a spinning object moving through air or another fluid.

Magnitude or size of a mathematical object is a property which determines whether the object is larger or smaller than other objects of the same kind.

Magnetohydrodynamics is the study of the magnetic properties and behaviour of electrically conducting fluids.

A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current.

Magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material.