공 분산(A statistical measure of the tendency of two variables to change in conjunction with each other. It is equal to the product of their standard deviations and correlation coefficients); 공변성Covariance(In programming languages, the ability to use a more derived type than that originally specified. Covariance in generic interfaces and delegates allows for implicit conversion of generic type parameters. Covariance is also supported for non-generic delegates for matching method signatures with delegate types)
