fXYst
fXYst is a fictional construct used in theoretical discussions of multivariate functions and dynamic systems. It denotes a family of four-argument functions f(X, Y; s, t) designed to capture how two primary variables X and Y interact under a state parameter s and a time parameter t. The notation emphasizes cross-variable interaction rather than independent effects.
Formally, each instance fXYst maps from domains D_X × D_Y × S × T to a codomain
Origins and usage. The term fXYst does not refer to a widely adopted mathematical formalism; it appears
Applications and implementation. In practice, fXYst can guide model design for systems where X and Y jointly
See also: multivariate function, interaction term, tensor, dynamic system.