This paper tries to give a general description of a thermodynamic cycle (whatever kind and number of transformations) as a function of a set of independent parameters characterising thermodynamic transformations, as well as of constraints imposed on the cycle by plant physical nature, lay-out and controls. An 'Associated Reversible Transformation' (A.R.T.), defined in the paper, is used to describe each real thermodynamic transformation of working fluid, similarly to well-known description of ideal gas adiabatic compression by means of a polytropic transformation, so that A.R.T. may be regarded as polytropics generalised. A simple gas cycle is used to present an application of A.R.T. in the field of energy Diagnosis, underlining usefulness of a complete set of independent parameters for cycle description. Further application in the fields of second law analysis and thermoeconomics are outlined in the concluding part of the paper. (c) 2004 Elsevier Ltd. All rights reserved.