What is a relative number?

A new family of numbers

So far, you have mainly used positive numbers (0, 1, 2, 3...). Relative numbers add an extra piece of information: the sign. A relative number consists of a sign (+ or -) and a distance from zero (the numerical part).

Examples:

• +5 is read as ‘plus five’
• -3 is read as ‘minus three’
• 0 is considered both positive and negative (special case)

What are they used for?

Relative numbers allow us to represent situations with two opposite meanings:

• a temperature of -5 degrees C (below zero)
• an altitude of -120 m (below sea level)
• a bank balance of -20 euros (a debt)

Important vocabulary

Term	Meaning
Positive number	A number preceded by the + sign (or without a sign)
Negative number	A number preceded by the -
Opposite of a	A number denoted as -a, the same distance from zero but with the opposite sign

The opposite of +7 is -7. The opposite of -4 is +4. The opposite of 0 is 0.

Common pitfall

Be careful not to confuse the “-” sign, which indicates a negative number, with the “-” sign used in subtraction. For example, in “5 – 3”, the sign indicates an operation, but in “-3”, the sign is part of the number itself.