Final answer:
Someone who is 70 years old would be classified as elderly, fitting into the 'young-old' subgroup according to the United States' age categorizations for older adults.
Step-by-step explanation:
Someone who is 70 years old would be classified as elderly. In the United States, the older adult population can be divided into subgroups based on their age: the young-old (approximately sixty-five to seventy-four years old), the middle-old (ages seventy-five to eighty-four years old), and the old-old (over age eighty-five). Considering this categorization, a 70-year-old falls into the young-old group. However, the term 'elderly' can broadly encompass all three categories.
There are key differences between the experiences and life circumstances of people at various ages within the elderly category. For instance, a 65-year-old might be healthier and more active compared to someone who is over 85. Yet, both are often considered elderly due to their chronological age, although they might be at different stages in terms of health and lifestyle.
Adulthood itself has various stages: early, middle, and late. While middle adulthood lasts from the mid-30s to the mid-60s, late adulthood generally begins at age 65. During late adulthood, people might confront increased health risks and undergo significant lifestyle changes as they transition into retirement and face the physical aspects of aging.