ml is the written short form of millilitre or millilitres, a small unit of volume. One millilitre is one thousandth of a litre — a tiny sip, or about a small cube of water. Medicine bottles, drink labels, and recipes use it all the time: 5 ml of syrup, a 330 ml can. You say “millilitres,” not “em-el,” unless you are spelling it. American spelling is milliliter, and the letters are often written mL; the amount is the same. It measures how much space a liquid takes, not how heavy it is.