An octopus has 8 legs. Or arms, depending on your point of view. The name octopus comes from Ancient Greek and is made up of 2 parts:

ὀκτώ = okto = 8
πούς = pous = foot/leg

So octopus is originally Greek. Remember that, it has implications later in this article!

Now when there is more than just one octopus confusion arises over how to make the plural. There are possibilities here and these three have been thrown about and used from time to time:

octopuses
octopi
octopodes

So which one is it?

Some Stats & Quotes

Take a look at Google n-grams (the graph is on the right) to start with and you’ll see that octopuses far outweighs the others in usage. Then comes octopi and then comes octopodes.

The Oxford English Dictionary agrees and lists octopuses, octopi and octopodes in that order but qualifies it by saying octopodes is rare. Other dictionaries pretty well stick to octopuses and occasionally one of them will throw in octopi or octopodes to keep things interesting.

Meanwhile Fowler’s Modern English Usage states that the only acceptable plural in English is octopuses, and that octopi is misconceived and octopodes pedantic.

Arguments against Octopi

Here’s where it gets interesting and where linguists get all hot and bothered.

Some people want to use octopi as a valid plural at all costs. Their argument goes like this:

1) Look at these words ending in -us which make valid and accepted plurals by changing it to –i:

alumnus > alumni
bacillus > bacilli
cactus > cacti
locus > loci
nucleus > nuclei
radius > radii
stimulus > stimuli
syllabus > syllabi

2) And since octopus ends in -us the plural can end in –i:

octopus > octopi

However, a great number of linguists get annoyed with this and object most strenuously. Their arguments go like this:

1) The first list above is made up of words which come from Latin where it’s perfectly acceptable to change singular -us into plural –i.

2) But octopus is Greek where it is grammatically incorrect to change -us into –i to make the plural!

What to do?

When there are 8, 16, 24, 32 or more legs on display, use the plural octopuses. That’s our advice.

If you use octopi you might make some pedants very angry (see above) and octopodes will make you sound like you’re showing off.

Useful Links

Singular and Plural Nouns‏‎ – all about singular and making correct plurals.

Spelling Singular & Plural Nouns – and about how to spell them.

Octopus: The thief of the deep – amazing pictures and facts about octopuses from the BBC.