Even Linnaeus inconsistently used polypi alongside octopodes, since he knew his Latin well, and the Romans used polypi, not polypodes. Latinized Greek plurals were often not consistent in their declensions, even for the ancient Romans. A difficulty with this argument is that the Latin predecessors, such as polypus, from which octopus was coined, actually used the second-declension plural form polypi. The argument goes that it would be a third declension noun in Latin, with stem octopod-, rather than a second declension noun, with stem octop. What matters is not how we would decline the word in Greek, but how we would decline the word in Latin. Yes, octopus ultimately comes from Greek roots, but it comes through Latinized Greek. The word comes from Greek, not Latin." First off, the word comes from Latin - if it were Greek, it would be oktopous (or maybe octopous, if we allow a little fudging in the transliteration). It doesn't matter how long it's been in the English language.
On the other hand, almost as soon as the word entered the English language, the plural octopi begins to be seen. Linnaeus did use the plural octopodes in his modern Latin and the root octopod- for example in the taxonomic order Octopoda.
The word octopus was coined by Linnaeus (the biologist) in the 18th century, based on a Latinized Greek word polypus.All of these suggest that there is a significant history of educated folks who would accept octopi as a reasonable plural. While the root octopod- is suggested by English words like octopod and the biological order Octopoda, there are also English words drawn from the root octop-, such as octopean, octopine, and octopic.It's exceedingly unlikely that our modern word came from these roots, as the etymology is explained below.) (There was a very rare adjective in Greek oktapous, also incredibly rare in Latin form as octipes, but it merely meant "eight-footed" and did not refer to the creature we now call an octopus.
The standard word for the Romans and Greeks to refer to the animal was polypus/polypous. The word octopus did not actually exist in either ancient Greek or ancient Latin, so appeal to a "native" plural is problematic.Some clarification is needed in the answers, though, since many people are under the impression that octopi is definitely wrong for historical reasons, while octopodes is apparently acceptable (even though almost no one aside from grammar fanatics has ever heard of it).Īfter reviewing the historical evidence, both octopi and octopodes have problems.Īside from the fact that octopi is a familiar plural to many and is indeed listed ahead of octopodes in almost all (if not all) dictionaries, generally following octopuses, there are strong historical reasons why octopodes should be suspect. As other answers have already pointed out, the correct English plural is octopuses.