The term ‘non-metric variation’ is generally taken to encompass any minor anomaly of skeletal anatomy not normally recorded by measurement. Non-metric traits are usually recorded as being either present or absent or, less often, scored according to their degree of development. As one might expect, given this definition, non-metric traits are a rather heterogeneous bunch, but one thing the variants discussed in this chapter do have in common is that none can be considered a sign of disease. Their presence in the skeleton causes no symptoms – you or I may have many of the non-metric traits discussed below in our own skeletons and be quite unaware of them.