Organism Function
aging Audio
ag·ing
Subclass of:
Growth and Development function
Definitions related to aging:
  • The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.
    NLM Medical Subject Headings
    U.S. National Library of Medicine, 2025
  • The gradual physiological changes that occur with the passage of time; includes from birth to death; may be used for any species.
    CRISP Thesaurus
    National Institutes of Health, 2006
  • The process of change in the structure and function of an organism that occurs with the passage of time.
    NCI
    U.S. National Cancer Institute, 2021
  • Aging is a gradual, continuous process of natural change that begins in early adulthood. During early middle age, many bodily functions begin to gradually decline.
    Merck Manuals
    Merck & Co., Inc., 2025
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This content should not be used in place of medically-reviewed decision support reference material or professional medical advice. Some terms may have alternate or updated definitions not reflected in this set. The definitions on this page should not be considered complete or up to date.