Hi guys. Would someone please explain to me what a cyclic integral is. I have seen them everywhere (especially in my Thermodynamics lectures) but my calculus book (1st year Uni) does not explain what they are and a search on googol has only led me to complicated examples. What I need is a layman definition (if it is possible) and if possible some sort of easy example that I can apply it to. Thanks heaps if anyone can give me a hand.

Yeah, this terminology is not really used in math, but is refered to as the integral around a closed path. These integrals are zero for a path in a conservative field for which the path encloses no singularities. Has to do with complex analysis in many ways. In thermodynamics, the work done by or on a system in a closed, reversible process is zero. It's really just another statement of the conservation of energy. In real life, a reversible process is like the massless pulley or the frictionless plane, ideal systems. These do not exist in reality, all process a non-reversible.