What is an integer?
An integer is a whole number that can be positive, negative or zero, such as −3, 0 or 42. Integers do not include fractions or decimals.
The set of integers is ..., −3, −2, −1, 0, 1, 2, 3, ... and continues forever in both directions. The word integer comes from Latin and means whole or untouched. Mathematicians use the symbol ℤ, from the German word Zahlen, meaning numbers.
Integers are used whenever quantities can go below zero, such as temperatures, elevations below sea level, bank balances and floors below ground in a building.
Rules for negative numbers
When multiplying or dividing integers, two numbers with the same sign give a positive result, and two with different signs give a negative result. So −3 × −4 = 12, while −3 × 4 = −12.
On a number line, integers are evenly spaced points, with negative numbers to the left of zero and positive numbers to the right. The distance of a number from zero is called its absolute value.
Did You Know?
Negative numbers were used in China more than 2,000 years ago, where calculators used red rods for positive numbers and black rods for negative ones.