The function of cognitive communication is to enable people and machines to acquire knowledge. The gain in knowledge lies in the information gained from the signals received. The links between information theoretical entropy and thermodynamic entropy and energy are explained in detail. This series of booklets is particularly valuable for lecturers and students of communication and cognitive sciences and border areas, as well as brain researchers, philosophers, media technicians, linguists and more. Everything is described in plain language for general understanding, but is also, at the same time, cast in precise mathematical terms without over-stretching.