Vector Calculus. By Dr. Michael Medvinsky, NCSU online lectures 03-04/2020. Definition: Vector Field is a function F that for each (x,y)\(x,y,z) assign a 2\3-dimensional vector, respectively: ( x , y ) = P ( x , y ) , Q ( x , y ) ( x , y , z ) = P ( x , y , z ) , Q ( x , y , z ) , R ( x , y , z )