An adult is typically an individual who have reached the age of majority, which is typically 18 or 21 years old, depending on the country or region. This is the age at which an individual is legally considered an adult and is typically granted full legal rights and responsibilities.
In the field of psychology, the concept of "adulthood" is often used to refer to the developmental stage that follows adolescence and is characterized by increased independence, responsibility, and self-awareness. During this stage of life, individuals typically experience significant changes in their relationships, roles, and responsibilities, as they move towards greater autonomy and self-sufficiency.
Research on adult development has focused on a wide range of topics, including cognitive and social development, career and family transitions, and physical and mental health. Understanding the psychological aspects of adulthood can help psychologists and other mental health professionals better understand and support the needs and challenges of adult clients.