Secondary sexual characteristics are the set of anatomical structures and features unique to males and females that are not directly related (and therefore secondary) to the production of sex cells (gametes).

Although in humans, the differences in male and female secondary sexual characteristics are more easily defined and determined, in many animals the differences are subtle. Regardless, the role of secondary sexual characteristics, especially with regard to the evolutionarily essential processes of mate identification and selection, can be extremely important.

Secondary sexual characteristics are generally distinguishing of gender in the human male and female. Accordingly, characteristics such as male facial hair or the enlarged breasts of a female may also carry importance in a particular social or religious culture.

The development of easily identifiable secondary sexual characteristics begins with the onset of puberty and continues throughout the teenage years into young adulthood.

In females...