For the formation of stationary waves, it is necessary that the medium should not be unlimited but it should have a boundary. The wave propagating in such a medium will reflect at the boundary and produce a wave of the same kind travelling in the opposite direction. The position of two waves will give rise to a stationary wave. At free end, transverse wave is reflected without change of phase. Hence as essential requirement for the formation of stationary wave is that the medium must be bounded having definite boundaries. In stationary waves, there are certain points of the medium, which are permanently at rest i.e., their displacement is zero throughout. These points are called nodes. Similarly, there are some other points which vibrate about their mean position with largest amplitude. These points are called antinodes.