Hair type falls into three categories, but there can be considerable differences even within these groups:

Caucasian-European: has an oval/flattened cross-section.
Asian: has a typically round cross-section.
African: has a very oval cross-section and tends to be tightly curled.

It is the shape, size and curve of the follicle that determines the profile of each hair strand and the cross-section of hair defines its type.

Dark-haired people have the thickest hair, followed by brunettes. Blondes may have the most hair but theirs is also the finest.

Hair growth and texture can be affected by health, nutrition, medication and even stress.