A
young adult is generally a person in the age range of 20 to 39 (or 40), although definitions and opinions, such as
Erik Erikson's
stages of human development, vary. The young
adult stage in human development precedes
middle adulthood. A person in the middle adulthood stage ages from 40 (or 41) to 64. In
old age, a person is 65 years old or older.