Kappa: Tenth letter of the Greek alphabet

In the system of Greek numerals, it has a value of 20. Letters that came from it include the Roman K and Cyrillic К.

The letter κ always stands for the sound "k" in Greek. It is customary to transliterate (re-write) κ as "c" in English, but this is somewhat problematic since c is pronounced as "s" before e, i and y (which does not happen in Greek).

The letter kappa is in geometry dash.

In mathematics, the lowercase ${\displaystyle \kappa }$ is used to represent the curvature of a curve, while the uppercase Κ is used to represent an ordinal number which is also a cardinal number.

• Thermal conductivity, represented by ${\displaystyle \kappa }$