A note on genetic distance.

Various definitions of 'genetic distance' and 'frequency distance' are considered, together with the purposes for which they are used. There are at least seven simple definitions of 'genetic distance' which agree closely with each other and with a Mahalonobis-type D2 for qualitative characters, whereas other proposed definitions are mostly based on quite different approaches. The Mahalanobis-type definitions are also related to random drift.