P

PSI (Pounds Per Square Inch)
In trucking, unit of measurement for tire air pressure, air brake system pressure and turbocharger boost.

PASCAL Pa
The pascal is the SI unit of pressure. One pascal is the pressure generated by a force of 1 newton acting on an area of 1 square metre. It is a rather small unit as defined and is more often used as a kilopascal [kPa]. See Metric Prefixes

It is named after the French mathematician, physicist and philosopher Blaise Pascal (1623-62).
More on Pascal

PICO p
A metric prefix meaning one million millionth or 10^-12. Commonly used in capacitance pF.See Metric Prefixes

POWER
Electrical energy measured according to voltage and current (normally watts). Power in watts equals volts times amperes for DC circuits. Mechanical power is also measured in watts.
Horsepower is not power (in physics terminology), but work.