x1 is a scalar in structure/set x2 with properties (potentially including magnitude, etc. in a given metric and coordinate system) x3; x1 is a simple number; x1 is a number that lacks
In some interpretations, for example, complex numbers may be scalars; in others (including mekso in a sense), they can be treated as two-component vectors (in which case "direction in the complex plane" and magnitude can be noted in properties x3).