The effect whereby the width of a spectral line is increased as a result of random movements within the region where the line originates. the velocity dispersion is related to the Doppler broadening by : $\dfrac{\delta \lambda}{\lambda}$ ~ $\dfrac{\delta v}{c}$ [[../Chapters/Topic 2 The spectral Universe]] [[Docent/S284 Astronomy]] [[../Chapters/Topic 3 Mapping the Universe]]