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Inexact Differential

An infinitesimal which is not the differential of an actual function and which cannot be expressed as

dz=\left({\partial z\over\partial x}\right)_y\,dx+\left({\partial z\over\partial y}\right)_z\,dy,

the way an Exact Differential can. Inexact differentials are denoted with a bar through the $d$. The most common example of an inexact differential is the change in heat ${\mathchar'26\mkern-12mud}Q$ encountered in thermodynamics.

See also Exact Differential, Pfaffian Form


Zemansky, M. W. Heat and Thermodynamics, 5th ed. New York: McGraw-Hill, p. 38, 1968.

© 1996-9 Eric W. Weisstein