My mechanics lecturer uses W for work done. My thermodynamics lecturer uses [tex]\Delta\x[/tex]When asked about this, I have been told that W actually refers to energy. I am not sure whom to believe. Also, in mechanics W is the work done by the system on the surroundings. In thermodynamics, work is defined the other way round. Why is that so? Won't that lead to mathematical errors when we use concepts from both branches to solve problems? Thanks in advance for any help!