availability Also known as bioavailability or biological availability. In some foodstuffs, nutrients that can be demonstrated to be present chemically may not be available, or only partially so, when they are eaten. This is because the nutrients are chemically bound in a form that is not susceptible to enzymic digestion, although it is susceptible to the strong acid or alkali hydrolysis used in chemical analysis. For example, the niacin in cereal grains, calcium bound to phytate, and lysine combined with sugars in the Maillard complex, are all biologically unavailable. See also lysine.

availability
1. The probability that a system will be capable of functioning according to specification at any point in time throughout a stated period of time. Compare reliability.

2. The ratio of available time to total time for a system in a given period.