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.
If you do not see any leaks here or puddles on the ground, your master cylinder may be leaking into the power booster. The only way I could tell you to check this is to disconnect the master cylinder from the brake booster and see if it is wet on the back side where it connects at the booster.