Ageing VS Aging
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Ageing (British English) or aging (American and Canadian English) is the accumulation of changes in an organism or object over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline. Ageing 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.
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The term "ageing" is somewhat ambiguous. Distinctions may be made between "universal ageing" (age changes that all perople share) and "probabilistic ageing" (age changes that happen to some, but not all people as they grow older). Chronological ageing, referring to how old a person is, is arguably the most straightfoward definition of ageing and may be distinguished from "social ageing" (society's expectations of how people should act as they grow older) and "biological ageing" (an organism's physical state as it ages). There is also a distinction between "proximal ageing" (age-based events that come about because of factors in the recent past) and "distal ageing" (age based differences that can be traced back to an early cause in a person's life.
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Additional defination according to Wikipedia, the free encyclopedia:
http://en.wikipedia.org/wiki/Ageing