A duet is a musical composition for two performers. In classical music, the term is most often used for a composition for two singers or pianists; with other instruments, the word duo is also often used. A piece performed by two pianists performing together on the same piano is referred to as "piano duet" or "piano four hands". A piece for two pianists performing together on separate pianos is referred to as a "piano duo".

"Duet" is also used as a verb for the act of performing a musical duet, or colloquially as a noun to refer to the performers of a duet. The word is also occasionally used in reference to non-musical activities performed together by two people.

In Renaissance music, a duet specifically intended as a teaching tool, to be performed by teacher and student, was called a bicinium (see Étude).

In computing, a uniform resource locator (URL) is a specific character string that constitutes a reference to an Internet resource.

A URL is technically a type of uniform resource identifier (URI) but in many technical documents and verbal discussions URL is often used as a synonym for URI.

The Uniform Resource Locator was created in 1994 by Tim Berners-Lee and the URI working group of the Internet Engineering Task Force (IETF) as an outcome of collaboration started at the IETF Living Documents "Birds of a Feather" session in 1992. The format combines the pre-existing system of domain names (created in 1985) with file path syntax, where forward slashes are used to separate folder and file names. Conventions already existed where server names could be prepended to complete file paths, preceded by a double-slash (//).

Every URL consists of some of the following: the scheme name (commonly called protocol), followed by a colon, two slashes, then, depending on scheme, a server name (exp. ftp., www., smtp., etc) followed by a dot (.) then a domain name (alternatively, IP address), a port number, the path of the resource to be fetched or the program to be run, then, for programs such as Common Gateway Interface (CGI) scripts, a query string, and an optional fragment identifier.