What’s the Plural of Tooth: Understanding Dentistry Terms

Tooth and Teeth — See the Pattern

Look at these sentences. Can you see when we use tooth and when we use teeth?

• The baby lost her first tooth last week.
• The dentist checked all my teeth today.
• I have a sore tooth at the back.
• Children start to lose their baby teeth around age six.

Did you see the pattern? We use tooth for one, and teeth for two or more. The word changes completely — we do not just add -s.

When to Use Tooth and When to Use Teeth

The rule is simple:

• Use tooth when you talk about one — “I chipped a tooth.”
• Use teeth when you talk about two or more — “She brushes her teeth every morning.”
• Do NOT add -s. “Tooths” is not correct in English.

This is called an irregular plural. Most English words add -s to become plural (cat → cats, dog → dogs). But “tooth” does not follow that rule. The “oo” sound in the middle changes to an “ee” sound.

Easy way to remember: Think of the word “feet.” Tooth → teeth works the same way as foot → feet. The “oo” always changes to “ee.”

How to Use Tooth and Teeth in Everyday English

• I need to see the dentist — my back tooth hurts. (= one specific tooth)
• Do you brush your teeth before bed? (= all your teeth)
• The child put her tooth under the pillow for the Tooth Fairy. (= one tooth)
• Sharks can grow new teeth all their lives. (= many teeth)
• He smiled and showed all his white teeth. (= the full set)

You are doing great. Now let us look at the mistakes many learners make.

The Most Common Mistake With Tooth and Teeth

Many English learners add -s and say “tooths” — this is completely normal. Even native speakers’ children say “tooths” when they are learning to talk. So if you make this mistake, you are not alone.

How to remember: Tooth and teeth follow the same pattern as foot and feet. If you can remember one, you know the other. Say it out loud: “one tooth, two teeth — one foot, two feet.”

Other words that change like this: foot → feet, goose → geese, man → men, woman → women, mouse → mice. These are all irregular plurals — the word changes instead of adding -s.

Test Yourself: Tooth or Teeth?

Choose the correct answer for each sentence. Click Check to see if you are right.

Keep Going — You Are Building Something

You just learned the plural of tooth. That is one more irregular plural you will never get wrong again.

But here is something interesting. You know that tooth becomes teeth. So what about foot? Does it follow the same “oo to ee” pattern? And if foot becomes feet, why does “boot” not become “beet”?

Next lesson: Plural of Foot — Why It’s Feet, Not Foots

Sources

1. Origin of tooth.
2. Synonyms for tooth.