In music, however, D.C. stands for Da Capo, and D.S. for Dal Segno.
These are navigation instructions, telling you to go back and repeat an earlier section.
Da Capo is Italian for “From the head”. It just means, go back to the beginning. Take it from the top.
Jazz musicians use “head” in English, to refer to the beginning of a piece where they play the most recognisable version of the tune.
Go back to the sign, and start again from there. Often a D.C. or a D.S. will be combined with a Coda. So the instruction is, “D.S. al Coda” – meaning, go back to the sign, play from there, but when you get to the “al Coda”, play or sing the Coda.
Very often if you don’t have a Coda you will have the word “Fine“* somewhere in the piece, and that is where you stop.
* Italian for End, pronounce fee-nay, not as in “Fine! I’ve had enough!” (flounces out)