In a physical context, scalar fields are required to be independent of the choice of reference frame.
Mathematically, a scalar field on a region U is a real or complex-valued function or distribution on U.
[1][2] The region U may be a set in some Euclidean space, Minkowski space, or more generally a subset of a manifold, and it is typical in mathematics to impose further conditions on the field, such that it be continuous or often continuously differentiable to some order.
Physically, a scalar field is additionally distinguished by having units of measurement associated with it.
In physics, scalar fields often describe the potential energy associated with a particular force.