What are secondary sexual characteristics?

Secondary sexual characteristics are physical features that develop during puberty and distinguish males from females, but are not directly involved in reproduction. In boys, these include facial and body hair growth, deepening of voice, broadening of shoulders, development of Adam's apple, and increased muscle mass. In girls, secondary sexual characteristics include breast development, widening of hips, growth of pubic and underarm hair, and redistribution of body fat. These changes are triggered by sex hormones—testosterone in males and estrogen in females—and typically begin between ages 10-14, marking the transition from childhood to adulthood.