What is defined as the natural decline of biological functions and adaptation to stress?

The concept of aging is understood as the gradual process through which biological functions deteriorate over time, along with the body’s ability to adapt to various stressors. Aging encompasses a wide range of physical, psychological, and social changes that occur as individuals grow older. This process is influenced by genetic, environmental, and lifestyle factors, leading to a lowered resilience to stress and an increased susceptibility to a variety of health issues.

In contrast, gerontology is the study of aging itself and encompasses the social, psychological, and biological aspects of the aging process, rather than defining the process. The physical changes of aging refer specifically to the observable transformations in the body, such as skin elasticity and muscle mass loss, while senescence indicates the process of deterioration with age at the cellular or organismal level but does not fully encompass the broader adaptations involved with the aging experience. Thus, aging is the most comprehensive term among the options that describes the natural decline in biological functions and the ability to adapt over time.