What is a quasi equilibrium. What is its importance in engineering?

When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times, it is called a quasi-static or a quasi-equilibrium process. A quasi-equilibrium process can be viewed as a sufficiently slow process that allows the system to adjust itself internally so that properties on one part of the system do not change any faster than those other parts. Engineers are interested in quasi-equilibrium process for two reasons. Firstly, they are easy to analyze. Secondly, work-producing devices deliver the most work when they operate on quasi-equilibrium processes. Engineer Ebrahim Anwar Kisswani.