P : the sixteenth letter of the English alphabet, is a nonvocal consonant whose form and value come from the Latin, into which language the letter was brought, through the ancient Greek, from the Phoenician, its probable origin being Egyptian. Etymologically P is most closely related to b, f, and v; as hobble, hopple; father, paternal; recipient, receive. See B, F, and M.

Example:
How do the fermi levels of P and n-regions of an unbiased P-n junction adjust to become equal?

Taxonomy
PADI, scuba diving, Dive Shop, Scuba Gear, scuba certification, scuba diving lessons, Dive Resorts, scuba diving vacations, scuba dive, scuba lessons, Scuba Diving Trips, scuba instructor, scuba diver, Dive, PADI Scuba Diving Courses, scuba dive equipment, scuba dive shop, Courses.

Defination from the web:
Official site for the Professional Association of Diving Instructors.