Editing Exact differential (section)

{{Short description|Type of infinitesimal in calculus}}
{{about| the concept from elementary [[differential calculus]]| the generalized advanced mathematical concept from [[differential topology]] and [[differential geometry]] | closed and exact differential forms}}

In [[multivariate calculus]], a [[differential (infinitesimal)|differential]] or [[differential form]] is said to be '''exact''' or '''perfect''' (''exact differential''), as contrasted with an [[inexact differential]], if it is equal to the general differential <math>dQ</math> for some [[differentiable function]]&nbsp;<math>Q</math> in an [[Orthogonal coordinates|orthogonal coordinate system]] (hence <math>Q</math> is a multivariable function [[Dependent and independent variables#In pure mathematics|whose variables are independent]], as they are always expected to be when treated in [[multivariable calculus]]).

An exact differential is sometimes also called a ''total differential'', or a ''full differential'', or, in the study of [[differential geometry]], it is termed an [[exact form]].

The integral of an exact differential over any integral path is [[Conservative vector field#Path independence|path-independent]], and this fact is used to identify [[state function]]s in [[thermodynamics]].