In practice, simple idealized thermodynamic cycles are usually made out of four thermodynamic processes.  Any thermodynamic processes may be used. However, when idealized cycles are modeled, often processes where one state variable is kept constant, such as:
* adiabatic (constant heat) 
* isothermal (constant temperature)
* isobaric (constant pressure)
* isochoric (constant volume)
* isentropic (constant entropy)
* isenthalpic (constant enthalpy)
Some example thermodynamic cycles and their constituent processes are as follows: