Cover
In telecommunication, cover is the technique of concealing or altering the characteristics of communications patterns for the purpose of denying an unauthorized receiver information that would be of value.Note: Cover is a process of modulo two addition of a pseudorandom bit stream generated by a cryptographic device with bits from the control message.
Source: from Federal Standard 1037C and from MIL-STD-188
In philately a cover is an envelope or package, typically with stamps that have been cancelled. The term dates from the practice of covering letters prior to the invention of envelopes. Complete covers, as opposed to a front or a piece, may be referred as an entire. A First Day Cover is typically an envelope with a postage stamp cancelled on its first day of issue. A Commemorative Cover has a commemorative design and special postmark to mark the date of a specific event.
In pop music a cover is a new version of a previously recorded song. Pop musicians may play covers as a tribute to the original performer or group, to win audiences who like to hear a familiar song, to increase their chance of success by using a proven hit or to gain credibility by its comparison with the original song. They may also do it simply because they enjoy playing it. See [1] for a database of covers.
A cover band (or covers band) is a band that plays only covers, which may be from a single band or artist (a tribute band) or from many different sources.
See also: cover version.
In mathematics, particularly topology and set theory, a cover is a collection of subsets of a set whose union is the whole set.
In combat cover can either refer to a barrier (usually already at the scene of battle) which can be used for protection or concealment, or it can refer to the shielding or protection of persons on the battlefield (usually on the move) by those with either superior training/equipment, or in a more secure position.