an informal abbreviation for one thousand used in expressions where the unit is understood, such as "10K run" (10 kilometers) or "700K disk" (700 kilobytes or kibibytes). Note that "K" is also the symbol for the kelvin (see below) and is often used as a symbol for the karat. Also note that the symbol for the metric prefix kilo- (1000) is actually k-, not K-. In computer science, K often represents 210 = 1024 (see below under kibi- and kilo-).
SOurce :- Unc.edu