Plural of campus... why isn't it campi?

Hello all,

This is my first post here, so please be kind. I have often wondered why the plural of campus (campuses) does not follow the pattern of similar words such as octopus, cactus, or radius(Octopi, cacti, and radii respectively).

Does anyone know if there’s a reason for this? Or should I just chalk it up as an exception to the rule?

Speaking of the rule… is there a rule in this instance?


There is indeed a reason for this–in Latin, nouns that are neuter (as opposed to masculine or feminine) that end in -us have the -i or -ii ending in the plural.

Besides the examples above, alumni and loci (plural of locus) follow this pattern. IIRC, campus means field in Latin and the plural is indeed campi. However, due to the fact that most folks nowadays have never taken Latin, there are a number of words where people commonly use the incorrect singular or plural form because they don’t know the rules or simply because it sounds better.

The most outstanding example I can think of here is that media is the plural of medium, yet people still sometimes refer to “mediums” or use “media” in the singular sense.

Feel free to toss corrections my way–I only took Latin for two years and that was several years ago!

Octopi is an anomalous word. You’re best off ignoring it.

Locus is an anomalous Latin word; it can be either masculine or neuter in the plural.

But, in general, I think one important difference is that campus does not mean in English what it means in Latin. Radius and alumnus both mean in Latin what they do in English, at least in one sense. So rather than being an English word which was borrowed from Latin, campus is an English word which borrowed a spelling from a similar, but different, Latin word.

Another example of this would be doctor, which is a Latin word meaning “teacher”. The plural of the Latin word doctor is doctores.

What if you had several cans of Puss 'n Boots?

Well, the English-following-standard-rules plural of any word is formed by adding -s or -es according to a few rules.

Contrary to the point above, second declension masculine Latin nouns that end in -us form a plural in -i. Other Latin nouns of third and fourth declensions form plurals in other ways: corpus, a neuter 3rd declension noun, gives corpora; manus, the technical term for hand or forepaw in biology based on the Latin word for hand, is fourth declension – the Latin plural is also manus (with a long U), and the English usage is generally to use manuses since the one sheep/two sheep no-change written Latin plural could easily be misunderstood.

“Octopi” is a peculiarity of English, based on a partial acceptance of a misunderstanding of the rule – an octopus is an invertebrate with “eight feet” or octo +pus, the latter being Greek, and the proper plural from Latin borrowing from Greek would be octopodes.

Shoot, that’s right. I should have caught that. Here’s an overview of forming Latin plurals:

First declension is easy. All the words (that are important) are feminine, and first-declension nouns in English should be easy to work with:

F: alumna -> alumnae
F: alga -> algae

Second declension can be either masculine or neuter, and we’ve already seen examples:

M: alumnus -> alumni
M: radius -> radii
N: medium -> media
N: bacterium -> bacteria

Third declension nouns are tricky. They can be any of the three genders (though I can’t think of any actual examples in English that use M or F), and their singluars and plurals tend to look rather different:

M: doctor -> doctores (not an English word)
N: opus -> opera
N: genus -> genera

Fourth and fifth declension are so rare, you seldom have to worry about them in Latin, much less English.

i remember a group of latin noun in the little ditty
'a quericus of a certain tribus sat on the porticus of her domus under the shade of a quericus with an acus in her manus.
these were irregular endings of the us us nouns
any chance of the campus being amongst this group.?
semper bufo!

The short answer, which does not I think contradict anything posted above by folks who actually know some Latin, is that English grabbed words from other languages willy-nilly, whenever the need arose (and not before); there was no systemic incorporation of Latin words into English. Therefore, some words got pulled in with their correct plurals in the original language, some didn’t. For instance, you bring an agenda to a meeting, not an agendum, although you would expect agenda to be the plural.


I always wondered the same thing about guys named “Rufus”.

And, the big question, why isn’t “i” the plural of “us”? See, it’s the other way around, eh, eh??

The plural of octopus is not octopi!!! Octupus has a Greek root and therfor is not subject to Latin pluralization, the correct plural is Octopuses. Though some people do mistakenly use the plural ‘octopi’, it is incorect.

An alternative plural of octopus is octopodes, which is the Greek plural form.

Hang on a sec. Does this mean that one ring of deep fried prawn is a scampus?

No, scampi is from Italian, not Latin, and the singular is scampo.


So one of them would be a scampo, based on the Italian source for the term.

And, even then, a deep fried prawn would not be a scampo, since the definition requires that it be broiled or sautéed.

I saw a really scary report on the news the other night about how people these days hardly ever stop for schoolbi that are unloading children, even when they have their lights flashing…

An interesting bit of trivium, but let me add a datum point: the second quericus should probably be quercus (oak tree), and the interesting point about that noun is: second declension nouns (such as dominus) are all masculine except for tree names (such as quercus) which are feminine.

Interestingly enough, bus just happens to come from a Latin word omnibus, which is not nominative, not a noun, and not even singular. Trying to weasel the “correct” plural out of it would be difficult indeed.

:smack: I can’t believe I mixed up neuter and masculine… at least I knew it was a non-feminine word.

Arnold Winkelried said:

Isn’t bellum a 2nd declension neuter noun?