P1: A curve defines a vector at point. P2: A function defines a covector at a point. F1a: A congruence of curves defines a vector field. F1b:Every vector field corresponds to a congruence of curves. Statements F1 are analogous to P1. F2a: A "congruence of functions" defines a covector field? F2b: Every covector field correspond to a "congruence of functions"? What, if any, are the correct statements F2 that would be analogous to P2, just as F1 is analogous to P1?