Aging 
The process of a system's deterioration with time.

Andropause 
A gradual decline in sex hormone levels over a period of years resulting in physiological and psychological changes.

Anti-oxidant 
A nutrient or chemical that reacts with and neutralizes oxidants, free radicals or chemicals that release free radicals. Antioxidants are also called free radical scavengers. Vitamins A, C, E and some of the B vitamins, beta-carotene, selenium and some key enzymes in your body are all antioxidants.

Apoptosis 
A form of cell death in which a programmed sequence of events leads to the destruction of cells without releasing harmful substances into the surrounding area. Apoptosis plays an important role in health by eliminating aged cells, unnecessary cells, and unhealthy cells.

Atrophy 
The dying or death, normally referring to a gland or organ.

Average life expectancy 
The age at which 50 percent of the members of a population have died, when plotted on a standard survival curve.  This statistic is normally calculated from birth, but may be recomputed in terms of expected years remaining at any age.

Average life span
The average number of years that members of a population live.

Cell senescence
The stage at which a cell has stopped dividing.

Chromosomes 
Double stranded DNA helixes.

DNA (Deoxyribonucleic Acid) 
The genetic blueprint that resides in the nucleus of every cell of every living organism ever studied.

Free radical
Molecules with a free or unpaired electron. Free radicals are produced in many different ways such as, normal metabolic processes, ultraviolet radiation from the sun, nuclear radiation and the breakdown in the body of spoiled fats. Free radicals have been implicated in aging, cancer, cardiovascular disease and other kinds of damage to the body.

Free-radical scavenger 
The cascade of chemical reactions that occurs when a free radical reacts with another molecule in order to gain an electron. The molecule that loses an electron to the free radical then becomes a free radical, repeating the process until the energy of the free radical is spent, or the reaction is stopped by an antioxidant.

Gene 
A specific sequence of nucleotides in DNA or RNA that is located usually on a chromosome and that is the functional unit of inheritance controlling the transmission and expression of one or more traits by specifying the structure of a particular polypeptide and especially a protein or controlling the function of other genetic material.

Genome 
The genetic material of an organism.

Geriatrics 
A branch of Internal Medicine concerned with the care and treatment of older persons and the treatment and amelioration of diseases of old age and frailty.

Gerontology 
The study of the elderly, and of the aging process itself. It is to be distinguished from geriatrics, which is the study of the diseases of the elderly. Gerontology covers the social, psychological and biological aspects of aging

Life expectancy 
The average life span of an individual.

Longevity 
Length of life.

Maximum life span
The greatest age reached by any member of a given species.

Mitochondria
Structures in cells that metabolize sugars into energy. Mitochondria also contain DNA, which is damaged by the high level of free radicals produced in the mitochondria.

Mutation 
A relatively permanent change in hereditary material involving either a physical change in chromosome relations or a biochemical change in the codons that make up genes.

Photoaging
The process initiated by sunlight through which the skin becomes drier and loses elasticity. Photoaging is being studied for clues to aging because it has the same effect as normal aging on certain skin cells.

Senility 
The aging related loss of mental faculties.