Any of various physical characteristics that appear in humans at puberty and in sexually mature animals and that differentiate between the sexes without having a direct reproductive function.
Any of the physical characteristics that differentiate male and female individuals, as distribution of hair or fat on the body, breast and muscle development, deepening of the voice, etc., that are not directly related to reproduction and usually appear at puberty.
Any of various physical characteristics that differ between the sexes but do not have a direct reproductive function, appearing in humans at puberty and in other animals at sexual maturity or during the mating season.
Any of the physical traits in a sexually mature animal that are specific to one sex but are not directly involved in the act of reproducing. Secondary sex characteristics are thought to have evolved to give an individual an advantage in mating by making the individual more attractive to mates or by allowing the individual to defeat rivals in competition for mates. Some secondary sex characteristics include the facial hair of the human male, the relatively prominent breasts of the human female, the antlers found only in the male of most species of deer, and the colorful plumage of the males of many species of birds. The appearance of secondary sex characteristics is determined by the sex hormones.