Availability is a measure of time during which a generating unit, transmission line, ancillary service or another facility is capable of providing service, whether or not it actually is in service. 
Property of availability and usability at the request of an authorized entity (Vlastnost přístupnosti a použitelnosti na žádost autorizované entity). 
Ensuring timely and reliable access to and use of information. 
The property of being accessible and useable upon demand by an authorized entity. 
Property of being accessible and usable upon demand by an authorized entity.