@wikipedia

A thermodynamic equation relating state variables in thermodynamic equilibrium which describe the state of matter under a given set of physical conditions, such as  pressure  $//<![CDATA[ \begin{array}{l}p\end{array} //]]>$, density  $//<![CDATA[ \begin{array}{l}\rho\end{array} //]]>$ (or  compressibility factor  $//<![CDATA[ \begin{array}{l}Z\end{array} //]]>$), temperature  $//<![CDATA[ \begin{array}{l}T\end{array} //]]>$ or internal energy  $//<![CDATA[ \begin{array}{l}U\end{array} //]]>$ and chemical structure.

It usually takes following forms:

See also

Natural Science / Physics / Thermodynamics

[ State of matter ] [ PVT ] 

[ Ideal Gas EOS ] [ Real Gas EOS ]

[ PVT EOS @model ]