In mathematics, the word sign refers to the property of being positive or negative. Every real number that is non-zero is either positive or negative, and therefore has a sign. Zero itself is without a sign, or signless. In addition to putting signs into real numbers, the word sign is used throughout mathematics to indicate parts of mathematical objects that mean positivity and negativity. Usually, if numbers are seen without a sign, they are seen as a positive number. Otherwise, a minus sign "" is appended before the number to indicate that the number is a negative of another number.
The word sign is also sometimes used to refer to various mathematical signs, such as the plus and minus signs and the multiplication sign.
Sign of a number
A real number is said to be positive if it is greater than zero, and negative if it is less than zero. The attribute of being positive or negative is called the sign of the number. Zero itself is not considered to have a sign.
In arithmetic, the sign of a number is often denoted by placing a plus or minus sign before the number. For example, +3 would denote a positive 3, and −3 would denote a negative 3. When no plus or minus sign is given, the main way of seeing it is that a number is positive.
The sign of any number that is not zero can be changed to positive using the absolute value function. For example, the absolute value of −3 and the absolute value of 3 are both equal to 3. In symbols, this would be written as |−3| = 3 and |3| = 3.
Sign of zero
The number zero is neither positive nor negative, and therefore has no sign. In arithmetic, +0 and −0 both mean the same number 0.
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