Secondary sexual characteristics are physical characteristics of an organism that are related to or derived from its sex, but not directly part of its reproductive system. These characteristics typically start to appear during puberty in humans and at sexual maturity in animals. Examples of secondary sexual characteristics in humans include:
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Females: Enlarged breasts, widened hips, pubic hair, and the development of a higher-pitched voice.
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Males: Facial hair, Adams apple, pubic hair, and the development of a deeper voice.
Secondary sexual characteristics are distinguished from primary sexual characteristics, which are present at birth and are comprised of the external and internal genitalia, including the penis and testes in males and the vagina and ovaries in females. During puberty, females experience increased breast development, with the breast buds enlarging to form the primary breast. In males, the voice deepens and pigmented axillary and facial hair appear, usually about two years after the emergence of pubic hair. Changes in primary and secondary sex characteristics are essentially complete by postpubescence, at which time the individual is fertile. Nonetheless, some changes in secondary sexual characters continue to occur in this phase.
