How do you make octopus plural? The answer is not so simple—and has actually been at the center of debate for longer than you may realize.
Look this question up and you’ll get three options listed: octopuses, octopi, and octopodes. Why three? Which one is correct?
These different endings are some examples of how English takes plurals from different languages. The word “octopus” is a Latinized form of the Greek word októpus, which translates to “eight foot.” But the word’s etymological history reveals why there’s often confusion around how the pluralized form should be spelled, and what we’re supposed to say when we’re describing multiple cephalopods at once. (Ironically, the octopus is a solitary creature.)
Let’s start with octopi. Many people don’t like octopi, and you will rarely see it in edited works, but it does occasionally appear. Octopi, which derives from Latin, is the oldest of the three plurals. “The -i ending comes from the belief that words of Latin origin should have Latin endings in English (while octopus may ultimately come from Greek it had a stay in New Latin before arriving here),” says Merriam-Webster.
If you’re thinking, “It has a Latin origin, so why wouldn’t its plural form be in Latin, too?” you’re not alone. But it’s not that simple. “The -us in octopus is not the Latin noun ending that switches to -i in the plural, but the Greek pous (foot),” as this Quartz article points out.
That brings us to the next ending, octopodes, which follows the Greek formation for plurals. This is the least-used ending, even though it may fit the word’s Greek origins best. “Octopodes stems from the belief that because octopus is originally Greek, it should have a Greek ending,” says Merriam-Webster.
However, the final option, octopuses, is the preferred plural when speaking and writing in English. Merriam-Webster notes that this plural emerged later in the nineteenth century, and has the attached -es ending to follow the English formation of plurals.
There you have it: The most commonly accepted plural usage for octopus is octopuses.
Correct: The clever octopuses snuck out of their tank at night.