In science, a field or field quantity is a physical quantity – represented by a scalar, vector, spinor, or tensor – that has a value for each point in space and time. An example of a scalar field is a weather map of surface temperatures, described by assigning a number to each point on the map. A map of surface winds, assigning an arrow to each point on a map that describes the wind speed and direction at that point, is an example of a vector field. Strain tensor, representing the deformation of matter caused by stress, is an example of a tensor field. Field theories, mathematical descriptions of how field values change in space and time, are ubiquitous in physics. For instance, the electric field is another vector field, while electrodynamics can be formulated in terms of two interacting vector fields at each point in spacetime, or as a single rank-2 tensor field.