Aging (British and Australian English) or Aging (American and Canadian English) is the accumulation of changes in an organism or object over time.] Aging in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of aging grow and expand over time, while others decline. Reaction time, for example, may slow with age, while knowledge of world events and wisdom may expand. Research shows that even late in life potential exists for physical, mental, and social growth and development. Aging is an important part of all human societies reflecting the biological changes that occur, but also reflecting cultural and societal conventions. Age is usually measured in full years — and months for young children. A person's birthday is often an important event. Roughly 100,000 people worldwide die each day of age-related causes.

An animal's life is often divided into various ages. Historically, the lifespan of humans is divided into Eight ages; because biological changes are slow moving and vary from person to person, arbitrary dates are usually set to mark periods of life. In some cultures the divisions given below are quite varied.

In the USA, adulthood legally begins at the age of eighteen, while old age is considered to begin at the age of legal retirement (approximately 65).

• Pre-conception: ovum, spermatozoon
• Conception: fertilization
• Pre-birth: conception to birth (pregnancy)
• Infancy: Birth to 1
• Childhood: 1 to 12
• Adolescence: 13 to 19
• Early adulthood: 20 to 39
• Middle adulthood: 40 to 64
• Late adulthood: 65+
• Death
• Post-death: decomposition

Ages can also be divided by decades

Source: WIKIPEDIA: www.en.wikipedia.org/wiki/Aging