‘Work expands so as to fill the time available for its completion. General recognition of this fact is shown in the proverbial phrase “It is the busiest man who has time to spare”.’
C Northcote Parkinson
A general dictionary defines availability as something that is ready for use or accessible when required. In ITIL, availability refers to the accessibility of the various infrastructure and services provided by IT services during the stated time periods.
The exact definition of availability is:
Ability of a configuration item or IT service to perform its agreed function when required. Availability is determined by reliability, maintainability, serviceability, performance, and security. ...