: the arithmetical symbol 0 or 0̸ denoting the absence of all
magnitude or quantity a: the point of departure in reckoning;
specifically: the point from which the graduation of a scale (as
of a thermometer) begins b: the temperature represented by the
zero mark on a thermometer Number and numeral of critical
importance in mathematics. Zero is known as the additive
identity because adding it to any number does not change the
number's identity, or value. The product of zero and any number
is zero; for most number systems the converse is truethat is, if
the product of two numbers is zero, at least one of them must
equal zero. The latter property is fundamental to the solution
of nearly every problem in mathematics. Division by zero is
undefined; efforts to deal with such divisions led to calculus.
Various punctuation marks were first used in Mesopotamia
beginning about 700 BC to indicate an empty space in positional
notation, but never at the end of a numberthe difference
between, say, 78 and 780 had to be under