Senescence refers to the process of aging or growing old. It is a state in which an organism, cell, or tissue loses its ability to function properly due to the passage of time and the accumulation of damage. Senescence can occur at different levels, such as cellular senescence (where cells lose their ability to divide), tissue senescence (where organs or tissues lose their functionality), and organismal senescence (where the entire organism experiences a decline in its abilities). The process of senescence is influenced by various factors, including genetics, environmental stressors, and cellular damage.