Whats the Plural of Octopus: Understanding the Correct Usage
Quick Answer
The plural of octopus is octopuses. You might also hear octopi or octopodes, but octopuses is the most common and correct form. Example: “We saw three octopuses at the aquarium.”
Octopus, Octopuses, Octopi — See the Options
The word octopus comes from Greek. It means “eight feet.” Because it comes from Greek (not Latin), the plural follows English rules. Look at these examples:
- The aquarium has five octopuses in the big tank. (standard English plural)
- We watched a film about octopuses that can open jars. (most common form)
- Some people say octopi, but this is based on a mistake. (informal, not recommended)
- The Greek plural would be octopodes, but almost nobody uses it. (very rare)
Did you see the pattern? Octopuses is the safe choice. Just add -es to the end, like you would with bus → buses.
| Singular | Standard Plural | Other Forms (less common) |
|---|---|---|
| octopus | octopuses | octopi, octopodes |
Why Do People Say Octopi? And Is It Wrong?
Many English words that end in -us come from Latin. For Latin words, you change -us to -i to make the plural:
- cactus → cacti
- fungus → fungi
- radius → radii
People see octopus ending in -us and think it must follow the same Latin rule. But octopus is a Greek word, not Latin. So the -i ending does not really fit.
The short answer: “Octopi” is not technically correct, but many people use it and most people will understand you. If you want to be safe, use octopuses. It is always right.
Easy way to remember: Octopus is Greek, not Latin. Greek words get the normal English -es ending. Just say octopuses.
The Rule in One Line: The plural of octopus is octopuses — just add -es.
How to Use Octopuses in Everyday English
- The children loved watching the octopuses change colour. (more than one octopus doing something)
- Octopuses are some of the smartest animals in the sea. (talking about the group)
- The diver saw two octopuses hiding in the rocks. (a specific number)
- Did you know octopuses have three hearts? (a fun fact about them)
- My daughter drew a picture of three octopuses for school. (everyday sentence)
You are doing great. Now let us look at the mistakes many learners make.
Two Mistakes to Avoid With the Plural of Octopus
Even native English speakers argue about the plural of octopus — so if you have been confused, you are not alone. This is one of the most debated plurals in the English language.
Mistake 1: Writing “octopi” in formal or academic writing
✗ The study looked at the behaviour of octopi in deep water.
✓ The study looked at the behaviour of octopuses in deep water.
How to remember: “Octopi” follows a Latin rule, but octopus is Greek. In formal writing, always use octopuses. It is what dictionaries recommend.
Mistake 2: Using “octopus” when you mean more than one
✗ We saw three octopus at the beach.
✓ We saw three octopuses at the beach.
How to remember: Unlike some animals (like sheep or fish), octopus does change in the plural. When there is more than one, always add -es.
Other words that end in -us with tricky plurals: cactus → cacti/cactuses, focus → foci/focuses, radius → radii/radiuses.
Test Yourself: Octopuses, Octopi, or Octopodes?
Choose the correct answer for each sentence. Click Check to see if you are right.
1. We saw five _______ at the aquarium today.
2. Look! One _______ is hiding behind that rock.
3. The ocean is home to many different _______.
4. The children counted six _______ in the big tank.
5. Scientists say _______ are some of the smartest sea animals.
Keep Going — You Are Building Something
You just learned the plural of octopus. That is one more tricky plural you will never get wrong again.
Octopus ends in -us, and the plural is octopuses. But what about the word species? It also ends in -s. Is the plural specieses? Or does it stay the same? And if it stays the same, how do you tell the difference between one and many?
Next lesson: What’s the Plural of Species?
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My name is Khamis Maiouf. I am the creator of the English Teacher Site, dedicated to providing valuable resources and insights for students around the world. With a passion for education and a commitment to helping students enhance their skills, I aim to make English teaching more effective and enjoyable for both educators and students.
