It's biological engines, right. Things that either produce or consume biological fuel to do different sorts of processes. Also, of course of key importance to understand what the, in that case, biological thermodynamics are.

但不只是我们制造的引擎,生物引擎也是如此,它们产生或消费生物燃料,来完成不同的过程，当然，这也是理解生物热力学的关键所在。

麻省理工公开课 - 热力学与动力学课程节选