Plasma waves are considered as an interconnected set of particles and fields which develop in a systematically recurring order. A plasma is a quasineutral, electrically conductive fluid. In the simplest case, it is comprised of electrons and a single species of positive ions, but it may also include several ion species including negative ions as well as neutral particles. Because of its electrical conductivity, plasma couples with electric and magnetic fields. This collection of particles and fields supports a wide variety of wave events.