A "15-year-old" refers to a person who is in their fifteenth year of life, typically in the middle of their teenage years. At this age, individuals often experience significant physical, emotional, and social changes. They may be in high school, where they begin to explore their interests and develop friendships that can last a lifetime. During this time, many 15-year-olds start to gain more independence and responsibility. They may participate in activities such as sports, music, or clubs, and some may begin to work part-time jobs. This age is also marked by a growing awareness of the world around them, including issues related to peer pressure, identity, and future aspirations.