Segue denotes a potentially smooth, unbroken transition between two sections of music or of anything that usually contains pauses or breaks, such as news items during a broadcast or subjects in a formal interview or conversation. Segue is both a noun and a verb and speakers may use it as such.
Segue comes from the Latin word sequo, which means to follow. It is the root of such words and phrases as non sequitur, sequential and subsequent. Segued and segueing are acceptable forms of the word. Interchangeable use with the word segway is not advisable. Segway is a trademarked word for a brand of electric scooter.
The segue sign in musical scores is the dal segno, which resembles an infinity sign turned vertically. The segno is the actual symbol that connotes the beginning of a separate piece of music or a smaller section within a large piece of music that the composer wishes to be repeated.
When the performer reaches the score notation dal segno, or D.S., she returns to the segno without stopping and repeats the whole section to the end, or al fine. Ornamentation and embellishment characterize the second time through, especially in baroque music.
All musical segues are some derivation of the dal segno. One example is the unbroken stream of music between the songs "I Would Die 4 U" and "Baby, I'm a Star" on Prince's 1984 studio album "Purple Rain." Although the key signature changes from minor to major, the precise beat-matching suggests a seamless transition and a return to the beginning, albeit with a new melody and lyrics.