What Are Negative Numbers?
Negative numbers are numbers less than zero. We write them with a minus sign (−) in front, like −5 or −10. On a number line, they sit to the left of zero, going down: −1, −2, −3, and so on, getting smaller the further left you go.
Think of a number line like a ruler standing upright. Zero is in the middle. Positive numbers (like 1, 2, 3) go up above zero. Negative numbers go down below zero.
Think of it like a lift (elevator) in a building. If the ground floor is zero, then floors above ground are positive numbers. Basement levels below ground are negative numbers: −1, −2, −3 for deeper basements.
When Do We Use Negative Numbers?
Negative numbers appear in real life more often than you might think. Here are some common examples:
Temperature: When it's cold outside, we use negative numbers. If it's −5 degrees Celsius, that means it's 5 degrees below freezing. Freezing point is zero degrees.
Money and Debt: If you owe someone £10, you might write that as −£10. Your bank account balance can go negative if you spend more money than you have.
Think of it like a game of snakes and ladders. If you start at zero and go backwards, you get negative scores. A score of −3 means you've gone three spaces back.
Height and Depth: Sea level is considered zero. Mountains above sea level are positive (like +500 metres). Places below sea level, like the Dead Sea, are shown as negative numbers (like −430 metres).
Time and History: Years before the birth of Jesus Christ are written as negative numbers in some systems. We call these BC (Before Christ) or BCE (Before Common Era).
Working with Negative Numbers
When you add or subtract negative numbers, follow these simple rules: subtracting a negative number is the same as adding a positive number. For example, 5 − (−3) is the same as 5 + 3 = 8.
Understanding negative numbers is a superpower in maths because they let us describe the whole world—hot and cold, rich and poor, high and low!