What does it mean?
When you count a group of things, each object must get one number name and only one. This idea is called one-to-one correspondence. It is like giving every child in a class exactly one sticker: no child gets two and no child is missed.
If you point at 6 apples and say "1, 2, 3, 4, 5, 6", you have matched each apple to one number, so there are 6 apples.
The three counting rules
Counting correctly uses three rules together:
| Rule | What it means |
|---|---|
| Stable order | Say the numbers in the same order every time: 1, 2, 3 … |
| One-to-one | Each object gets exactly one number. |
| Cardinality | The last number you say tells how many there are in all. |
So if your counting ends at "8", there are 8 things, even if you counted them in a different order.
How to count carefully
- Organize the objects. Put them in a line or a row so you can see where you started.
- Touch or move each object as you say its number. Sliding objects across to a "counted" pile is a great way to stop yourself counting them twice.
- Say one number for each touch. Your voice and your finger should move together.
- Stop when every object has been counted.
- Say the total: "There are 7."
Counting things you can’t move
Sometimes the objects are in a picture or stuck in place. Then you can:
- Cross each one off with a pencil as you count.
- Count across each row from left to right, like reading.
- Use a counter (a small block) to mark the ones you have done.
Worked examples
Example 1: You point to 6 apples and say "1, 2, 3, 4, 5, 6." How many apples are there?
The last number said is 6, so there are 6 apples.
Example 2: Mia counts 5 ducks but says "1, 2, 3, 4, 5, 6, 7" because she touched two ducks twice. What went wrong?
She broke the one-to-one rule. Each duck must get just one number. The correct total is 5.
Example 3: Count the stars: ★ ★ ★ ★ ★ ★ ★ ★
Point and say 1 to 8. There are 8 stars.
Common mistakes
- Counting an object twice, or skipping one, especially in a messy pile.
- Your words running faster than your finger, so you say more numbers than there are objects.
- Recounting from 1 when asked "how many?" instead of remembering the last number.
Try it yourself
- How many: ■ ■ ■ ■ ■ ■ ■?
- Sam counts 4 cars and says "1, 2, 3, 4." How many cars are there?
- Why is it a good idea to push each counted toy to one side?
Answers: 1) 7 2) 4 3) So you don’t count the same toy twice or miss one.
Quick recap
- Every object gets exactly one number name.
- Touch or move each object as you count.
- The last number you say is the total.