Editing Invariant (physics) (section)

==Informal usage==
In the field of [[physics]], the [[adjective]] '''''covariant''''' (as in [[covariance and contravariance of vectors]]) is often used informally as a synonym for "invariant". For example, the [[Schrödinger equation]] does not keep its written form under the coordinate transformations of [[special relativity]]. Thus, a physicist might say that the Schrödinger equation is ''not covariant''. In contrast, the [[Klein–Gordon equation]] and the [[Dirac equation]] do keep their written form under these coordinate transformations. Thus, a physicist might say that these equations are ''covariant''.

Despite this usage of "covariant", it is more accurate to say that the Klein–Gordon and Dirac equations are invariant, and that the Schrödinger equation is not invariant. Additionally, to remove ambiguity, the transformation by which the invariance is evaluated should be indicated.