You may say “to-may-to” while I say “to-mah-to,” but let’s call off any arguments about the plural for octopus right now. Make no mistake. The cephalopods do have eight tentacles and there may be three ways to describe a group of them, but only one is technically correct.
While “octopi” has become popular in modern usage, it’s wrong. The letter “i” as a suffix to indicate a plural noun only applies to words with Latin roots, like “cacti” for more than one cactus. But octopus is derived from Greek, so the proper pluralization in this case would be “odes” if it was ever used. However, this particular word happens to employ a classic English formulation, and affixing a simple “es” at the end of octopus will do, according to grammar experts.
Word nerds who prefer “octopi” love to correct those who use “octopuses.” I know this from experience because I write a lot of stories about octopuses and, as a result, have gotten many messages about how I need to fix my English.
This is an error of the sort known to grammarians as a “hypercorrection.” A hypercorrection is the erroneous use of a word form or pronunciation based on a false analogy with a correct form. These mistakes are often the result of linguistic pretensions, a desire to sound particularly erudite that ends up going awry.
As Steven Pinker puts it in his 1999 book Words and Rules, “[T]he attempt to foist ‘proper’ Greek and Latin plurals has bred pseudo-erudite horrors such as axia (more than one axiom), peni, rhinoceri, and [octopi]. It should be…octopuses. The -us in octopus is not the Latin noun ending that switches to -i in the plural, but the Greek pous (foot).”
Hypercorrections are almost as common as word nerds. Lawyer, author, and dictionary editor Bryan Garner once wrote a post on Law Prose about subpoenas, for example, and many readers had the audacity to suggest that the master of grammar had erred when he failed to pluralize the word “subpoena” as “subpoenae.” The hyper-correctors got theirs when he responded with a correction of his own.
The English word subpoena, Garner explained, is derived from the Latin phrase sub poena, meaning “under penalty” or “under pain.” The editor wrote, “So the false Latin plural subpoenae is a hypercorrection and, in fact, not a Latin word at all. Two similar examples of hypercorrection are octopi for octopuses and ignorami for ignoramuses.”
Moral of the story? Reasonable minds may differ on matters of taste and style but when it comes to grammar and pluralizing, let’s not be ignoramuses who insist on using the word octopi.