The octopus is a highly intelligent animal, but does it know that he know its etymology and plural?


As the word octopus ends in us, it is very tempting to assume that it’s of latin origin, such as nucleus (plural nuclei) or alumnus (plural alumni) and that its plural should then be octopi.

The usual plural in English is actually octupuses, which would not be the only case where an English plural form is used. For example both forms are used for cactus (plural cactuses/cacti) and focus (plural focuses/foci).

The twist in this story though, is that octopus actually derives (through scientific Latin), from the ancient Greek ὀκτώπους (oktopous or “eight-footed”), which means that the correct plural form should be octopodes according to the Greek rules. 

In any case, English dictionaries don’t seem to agree, and we found the following:

  • Merriam Webster: octopuses or octopi
  • Oxford English Dictionary: octopuses (“The standard plural in English of octopus is octopuses. However, the word octopus comes from Greek, and the Greek plural form octopodes is still occasionally used. The plural form octopi is mistakenly formed according to rules for Latin plurals, and is therefore incorrect.“)

Octopus parachutes down on prey, Red Sea