A measure of the acidity of a substance in an aqueous solution. Pure water has a pH value of 7 and is classified as neutral. Below 7 is acid and above 7 is known as basic. The scale is from 0 (strong acid) to 14 (strong base).

The time span between the start and end of a single wave moving from zero to positive and negative positions and returning to zero.

Sensor that indicates camshaft position and hence where the engine is in its cycle.

There are a number of phases of injection: fill phase, spill phase, injection phase and the pressure reduction phase.

See Phosphor Bronze.

A process used by vehicle body manufacturers which results in the formation of a layer of zinc, iron, or manganese phosphate crystals on the surface of the part to be painted. In modern vehicle construction plants, phosphating is achieved by complete body immersion.

A material that can absorb oil making it ideal for making bushes/bearings.

An acid commonly used as a catalyst to speed up the cure of Etch primers and some baking finishes, usually alkyd/nitrogen resin combinations. Also a cleaner used for removing surface corrosion from ferrous metals.

The generation of an electrical current by light shining on certain materials such as some semiconductor devices. Photoelectric cell, photodiode or phototransistor.

A transistor that is operated by light.