Terminal hairs are thick, long, and dark, as compared with vellus hair. During puberty

Puberty

Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body. These parts will have different levels of sensitivity to androgens, primarily of the testosterone family.

The pubic area is particularly sensitive to such hormones, as are the armpits which will develop axillary hair. Pubic and axillary hair will develop on both men and women, to the extent that such hair qualifies as a secondary sex characteristic

Secondary sex characteristic

Secondary sex characteristics are features that distinguish the two sexes of a species, but that are not directly part of the reproductive system. They are believed to be the product of sexual selection for traits which give an individual an advantage over its rivals in courtship and aggressive...

, although males will develop terminal hair in more areas. This includes facial hair

Facial hair

Facial hair is a secondary sex characteristic of human males. Men often start developing facial hair in the later years of puberty or adolescence, approximately between 17–20 years of age, and most do not finish developing a fully adult beard until their early 20s or even later...

, chest hair

Chest hair

The term chest hair is generally used to describe hair that grows on the chest of human males, in the region between the neck and the abdomen. Chest hair, which is a secondary sex characteristic, develops during and after puberty...

, abdominal hair

Abdominal hair

The term abdominal hair refers to the hair that grows on the abdomen of humans and non-human mammals, in the region between the pubic area and the thorax . The growth of abdominal hair follows the same pattern on nearly all mammals, vertically from the pubic area upwards and from the thorax...

, leg

Leg hair

Leg hair is hair that grows on the legs of humans, generally appearing at the onset of adulthood.Male legs are most often hairier than female ones. The amount of hair on an individuals legs can depend on their ethnic background...

 and arm hair, and foot hair. Human females on the other hand can be expected to retain more of the vellus hair.