Availability

Ensuring timely and reliable access to and use of information.
SOURCE: SP 800-53; SP 800-53A; SP 800-27; SP 800-60; SP 800-37; FIPS 200; FIPS 199; 44 U.S.C., Sec. 3542

The property of being accessible and useable upon demand by an authorized entity.
SOURCE: CNSSI-4009