Adulthood refers to individuals who have completed their growth and development and are ready to assume roles in society. It is typically divided into three stages: early adulthood from ages 18-40 which involves adjustments to new lifestyles and roles; middle adulthood from ages 40-60 as a time of achievement and stress; and late adulthood from age 60 onward as a period of decline and preparation for the end of one's life span. Adulthood varies across cultures but generally involves taking on new social expectations and developing new attitudes and interests to match evolving roles and responsibilities.