A physical quantity assigned to every point in spacetime, mediating forces and interactions.
gravitational field: generated by mass, described by gravity and general relativity
electromagnetic field: generated by charges and currents — see electromagnetism
quantum fields: fundamental entities in quantum mechanics; particles are excitations of fields
scalar fields (Higgs, temperature), vector fields (electric, magnetic), tensor fields (metric of spacetime)
field equations (Maxwell's, Einstein's) govern how fields evolve and interact
energy and momentum are carried by fields themselves
the field concept replaces action-at-a-distance with local, propagating interactions