* In statistics: Kappa (κ) most commonly represents Cohen's kappa, a statistic used to measure the agreement between two raters who each classify a number of items into a limited number of categories. It's a measure of inter-rater reliability. There isn't a "full form" for Cohen's kappa beyond that description.
* In physics and other sciences: Kappa can represent various constants, coefficients, or other variables depending on the specific equation or field of study. There's no single full form in these instances.
* In mathematics: It can be used as a variable or a constant, with no fixed full form.
Therefore, you need to specify the context in which you encountered "kappa" to determine its meaning. If you're referring to Cohen's kappa in statistics, that's the most likely interpretation.