Octopuses, Octopi or Octopodes?
An octopus is an eight-armed sea creature with remarkable intelligence. Its plural has been argued over for a century, and one popular answer is wrong.
An octopus is a soft-bodied mollusc with eight arms, three hearts and blue blood. The plural argument has a clear answer: the word is Greek, not Latin, so *octopi* applies a Latin ending to a Greek word. *Octopuses* is standard English; *octopodes* is the Greek form and mostly a joke among people who know.
- An eight-armed marine mollusc. *An octopus in the rock pool.*
- Something with many branches (figurative). *An octopus of a bureaucracy.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | octopus | A common octopus. |
| Plural | octopuses | Three octopuses. |
| Plural (Greek) | octopodes | Octopodes, rarely. |
| Related | cephalopod | Cephalopods include squid. |
| Related | tentacle | Arms, not tentacles. |
How it is used in a sentence
- Octopuses can open jars to reach food.Documented in laboratories.
- The octopus changed colour in a second.Using pigment cells in the skin.
- It has arms, not tentacles.Squid have two tentacles and eight arms.
Facts about octopuses
- Three hearts — two for the gills, one for the body
- Blue blood — copper-based haemocyanin instead of iron
- Nine brain-like centres — a central brain plus one per arm
- Colour blind — yet expert at matching their surroundings
- Short lives — most species live only one to two years
From Greek *oktopous*, eight-footed, from *okto*, eight, and *pous*, foot. English usually pluralises borrowed words with *-es* once they are naturalised, which is why octopuses is standard.
Is *octopi* wrong?
It is widely used but etymologically confused: it puts a Latin plural on a Greek word. Octopuses is safest.
Arms or tentacles?
Octopuses have eight arms. Tentacles are longer, with suckers only at the tip, and belong to squid and cuttlefish.