Clausius theorem

== English == === Etymology === Developed by German physicist and mathematician Rudolf Clausius. === Proper noun === the Clausius theorem A theorem stating that, for a thermodynamic system exchanging heat with external reservoirs and undergoing a thermodynamic cycle, ∮ δ Q T surr ≤ 0 , {\displaystyle \oint {\frac {\delta Q}{T_{\text{surr}}}}\leq 0,} , where δ Q {\displaystyle \delta Q} is the infinitesimal amount of heat absorbed by the system from the reservoir, and T surr {\displaystyle T_{\text{surr}}} is the temperature of the external reservoir (surroundings) at a particular instant in time.