Availability

n. obtainability, accessibility, attainability

For the thermodynamic function availability, in the sense of available useful work, see exergy.For availability as a form of cognitive bias, see availability heuristic.In telecommunications and reliability theory, the term availability has the following meanings: 1. The degree to which a system, subsystem, or equipment is operable and in a committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time. Simply put, availability is the proportion of time a system is in a functioning condition.
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Noun
1. the quality of being at hand when needed
(synonym) handiness, accessibility, availableness
(antonym) inaccessibility, unavailability
(hypernym) convenience
(hyponym) command
(attribute) accessible

(n.)
The quality of being available; availableness.
  

(n.)
That which is available.
  

1. The degree to which a system, subsystem, or equipment is operable and in a committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time. Note 1: The conditions determining operability and committability must be specified. (188 ) Note 2: Expressed mathematically, availability is 1 minus the unavailability. 2. The ratio of (a) the total time a functional unit is capable of being used during a given interval to (b) the length of the interval. Note 1: An example of availability is 100/168 if the unit is capable of being used for 100 hours in a week. Note 2: Typical availability objectives are specified in decimal fractions, such as 0.9998.