Kappa is a measure of the sensitivity of the price of an option contract to changes in the volatility of the underlying asset.
Kappa, also called vega, is one of the four basic Greek risk measures, named after the Greek letters that stand for them.
Kappa measures risk by calculating the amount by which the price of an option contract changes in response to a 1% change in the underlying asset’s implied volatility.
This set of risk measures - kappa, theta, gamma, delta - shows how sensitive an option is to depreciation in time value, changes in implied volatility, and movements in the price of the underlying security.