Geriatrics differs from standard adult medicine because it focuses on the unique needs of the elderly person. The aged body is different physiologically from the younger adult body, and during old age, the decline of various organ systems becomes manifest. Previous health issues and lifestyle choices produce a different constellation of diseases and symptoms in different people. The appearance of symptoms depends on the remaining healthy reserves in the organs. Smokers, for example, consume their respiratory system reserve early and rapidly. It is important to note the difference between geriatrics, the care of aged people, and gerontology, which is the study of the aging process itself. The term geriatrics comes from the Greek γέρων geron meaning "old man", and ιατρÏŒς iatros meaning "healer". However, geriatrics is sometimes called medical gerontology.