A song is a single musical composition with a melody and, frequently, words performed by a performer. The lyrics of a song are the words of the song as a whole, and they may comprise verses that tell a story or move a story along, as well as refrains, or brief phrases repeated at the conclusion of each verse. A song's melody is the sequence of tones (or tone-groups) that make up the music. In Western art music, a song consists of a series of musical sections, or stanzas, which are usually delineated by key signatures. Each section has a distinctive form that reflects its function in the larger structure of the song. In addition to these structural elements, songs often include other recognizable features, such as bridges, preludes, postscripts, etc. That said, not all songs follow this basic format; many are simply blocks of music without any particular structure or design. The word "song" comes from the French "songe", which means "dream" or "vision". Although dreams are often very beautiful, sad, or exciting, they do not always have a clear beginning, middle, and end. Songs, on the other hand, are always complete in themselves, although they may contain various sections that have different purposes.