0 ( zero ) is a number , and the numerical digit used to represent that number in numerals . It fulfills a central role in mathematics as the additive identity of the integers , real numbers , and many other algebraic structure . As a digit, 0 is used as a placeholder in place value systems . Names for the number 0 in English include zero , nought (UK), naught , nil , or—in contexts where at least one adjacent digit distinguishes it from the letter "O"— oh or o . Informal or slang terms for zero include zilch and zip . Ought and aught , as well as cipher , have also been used historically. The word zero came into the English language via French zéro from the Italian zero , a contraction of the Venetian zevero form o...