MANIFOLD:
A conductor that provides multiple connection ports. A fabricated system of passages to which various components are attached to form a working assembly or sub-assembly. See hydraulic manifolds.

MANUAL CONTROL:
A control actuated by the operator.

MANUAL OVERRIDE:
A way of manually actuating an automatically controlled device.

MASS FLOW RATE:
The mass of fluid per unit of time passing through a given cross-section of a flow-passage in a given direction.

MECHANICAL ACCUMULATOR:
A hydraulic component that transfers mechanical energy to trapped fluids. Mechanical accumulators include dead-weight and spring-loaded accumulators.

MECHANICAL CONTROL:
A control actuated by cams, gears, linkages, screws, or other mechanical elements.

MECHANICAL POWER:
Energy created by the physical interaction of instruments or tools.

METER-IN:
To regulate the amount of fluid flow into an actuator or system.

MICRON:
1/1000th of a millimetre or 0.00003937 inches. The measure used to determine the particle size of contaminants in a fluid system.

MICRON RATING:
The size, in microns, of the particles a filter will remove?

MISCIBLE:
Capable of being mixed in any concentration without separation

MOTOR:
A device which converts hydraulic energy into rotary motion and force, either fixed or variable. See The Ultimate Guide to Hydraulic Motors.

MUFFLER:
A mechanical device for reducing gas flow noise, by providing a complex path for exhaust of air from a pressurised chamber.