The above answer is too general-- describing thermodynamic equilibrium. Thermal equilibrium means there is a well-defined and constant temperature for the system and its (local) environment.
-
A system is in thermal equilibrium if detailed balance is obtained. Detailed balance implies that every process in the system is exactly balanced by its inverse process. As a result, there is no net effect on the system.
Go here for more details.
Hope this has helped
Go here for more details.
Hope this has helped