Metabolism (noun)

1. The chemical processes that occur within a living organism in order to maintain life.
2. The rate at which an organism burns calories in order to sustain its bodily functions.

Origin:

Late 18th century: from german metabolismus, from metabole "change", from meta- "change" + -bolos "throw".

Examples:

1. Metabolism is the process by which the body converts food into energy.
2. A person's metabolism slows down as they age.
3. Certain medications can affect the metabolism of the body.
4. Metabolism is the sum total of all the chemical reactions in the body.
5. The metabolism rate is used to calculate how many calories the body burns daily.