# Classification of non-mechanical waves

Transverse and longitudinal waves are classified according to the direction of propagation of wave motion and direction of oscillations of particles of the medium. But in the case of non-mechanical waves there is no medium, so there are no particles of a medium to oscillate. In this case how does one classify longitudinal and transverse waves?

The obvious example is the electromagnetic field: In an electromagnetic wave, the $\vec{E}$ and $\vec{B}$ fields are vector fields, i.e.\ they have a direction, and they are orthogonal to the direction of propagation.