Definition of a Function. A function is a relation for which each value from the set the first components of the ordered pairs is associated with exactly one value from the set of second components of the ordered pair. Okay, that is a mouth full.
Master cylinder without booster. Single bore master cylinders: These unboosted hydraulic Master Cylinders are actuated by foot effort, via the brake pedal. The brake pressure is related to actuation force and depends on the piston bore size: the smaller the bore, the higher the pressure.
The master cylinder converts the mechanical force from the brake pedal into hydraulic pressure. When the brake pedal is depressed, the master cylinder piston moves forward and pushes the brake fluid ahead of it. Since the brake lines and wheel cylinders are filled with brake fluid, the piston acts on a solid column of fluid.