Morning +5°, Night −3°
Have you ever seen a thermometer drop below zero on a freezing day? Numbers can go below zero too!
Here's a number line. Zero sits right in the middle — it's our starting point.
Numbers to the right of zero are positive. They count up: one, two, three, and so on.
Say the morning temperature is five degrees above zero. We mark plus five to the right of zero.
Numbers to the left of zero are negative. They count down below zero.
By night, it drops to three degrees below zero. We write negative three, with a little minus sign in front.
Notice: negative three and positive three are the same distance from zero — just opposite directions.
We use negative numbers everywhere: cold temperatures, money owed, or depths below sea level.
Positive numbers go up from zero, negative numbers go down. Together, they let us describe the whole world!