The plural of octopus can be octopuses, octopi or octopodes, and dictionaries accept all three, but octopuses is the most common one today.
🌀 The Weird Part
Most English plurals are easy: add an -s or -es. But octopus has three possible plurals, and each one follows the rules of a different language.
Even the ending of the word has a story: that -pus is not just a random bit.
Where does the word come from?
Octopus comes from Greek: okto means "eight", and pous means "foot". So an octopus is, quite literally, an eight-foot animal. English took the word through New Latin, the Latin that scientists wrote in.
So that -pus is not a mistake: it means foot. It is the same Greek word you can find in platypus, which means "flat foot".
Plural 1: octopuses
Octopuses is the plural a normal English word would get: add -es after an s.
The aquarium has three octopuses.
This is the most common form today, and it is the safest one to use.
Plural 2: octopi
Octopi treats the word as if it were Latin. Many Latin words that end in -us get -i in the plural: cactus → cacti, fungus → fungi.
People started to say octopi because they thought that every word that arrived through Latin should take a Latin plural. It is the oldest of the three forms.
Two octopi were hiding behind the rocks.
The funny part is that octopus was a Greek word to begin with. So octopi is a Latin-style plural on a word that started out Greek.
Plural 3: octopodes
Octopodes follows the word's real Greek origin. It is correct in the Greek way, but it is rare.
The scientist wrote about the octopodes of the deep sea.
You will mostly meet it in books about words. In everyday English, almost nobody says it.
So which should I use?
- Use octopuses in normal speech and writing. It is the most common, and nobody will blink.
- Octopi is also accepted. You will hear it, and it is not wrong.
- Octopodes is for when you want to impress someone, or you are writing about Greek words.
Do not let anyone tell you that one of them is "the only correct one". Dictionaries accept all three.
⚠️ Common Mistakes
Do not leave it unchanged.
❌ Three octopus swam past.
✅ Three octopuses swam past.
Octopi is a plural, not a singular.
❌ I saw an octopi at the aquarium.
✅ I saw an octopus at the aquarium.
💬 In a Conversation
Sam: How many octopi are in the tank?
Mia: Three octopuses.
Sam: You said it differently from me.
Mia: Both are allowed. There are also octopodes.
Sam: Three words and no octopus has complained yet.
Mia: They are busy with eight things each.
⏳ The OddLingo Timeline
Greek oktopous ("eight-footed") → New Latin octopus → English octopus → octopi (the oldest plural, Latin pattern) → octopodes (the Greek plural) → octopuses (the regular English plural, now the most common).
🥡 The OddLingo Takeaway
One animal, three plurals, three languages: octopuses (English), octopi (Latin style) and octopodes (Greek). Pick octopuses and you will always be understood.
For more plurals that refuse to behave, see Mice vs Houses and Sheep, Deer and Fish.