Potential and kinetic are a very general classification of energy forms As stated in the present version of the article these are mostly useful in mechanics Based on the fact that a photon has no mass the equations that are given in the present definition of kinetic energy are not applicable to electromagnetic radiation I must say I agree with Andries Also this article is part of an encyclopedia Why should it be limited to the basic definitions of kinetic and potential energy forms and I see no reason why we are trying to associate energy forms as to being only potential or kinetic I like the work done by Bensaccount but I think it needs to be elaborated Electrical energy for example has both forms of potential and kinetic energies According to Principles of science 1966 the most common forms of energy are mechanical energy chemical energy heat energy sound energy compressional waves light energy electromagnetic radiation electrical energy and nuclear energy I think if someone would like to expand on these it would be benificial to everyone Louis May 30 2004