K : the eleventh letter of the English alphabet, is nonvocal consonant. The form and sound of the letter K are from the Latin, which used the letter but little except in the early period of the language. It came into the Latin from the Greek, which received it from a Phoenician source, the ultimate origin probably being Egyptian. Etymologically K is most nearly related to c, g, h (which see).

Example:
How do you tell a pentax K mount lens from other lenses?

Taxonomy
K&N, Oil Filters, Air Filters, high-flow, K&N Engineering, motorcycle, Warranty, High Performance, racing, Air Intakes, horsepower, filters, kits, reusable, Vehicle, ATV, K&N FilterCharger, Mile Limited.

Defination from the web:
High performance air and oil filters for cars, trucks, motorcycles, ATVs, marine, racing and more. Bolt-on performance horsepower.