Why are hippopotamuses hippopotami and cactuses are cacti, but censuses aren't cenci?

Question

Just wondering what the rule is that dictates the plural of census to be censuses.

Answer 1

Actually all those three words are from Latin. Hippopotamus is late Latin, after the Greek 'hippo-potamos', 'horse of the river'; cactus is a Latin word after the Greek 'kaktos'; census is a pure Latin word from the verb 'censere', 'to rate, assess'.

Nouns in Latin ending in -us may be in one of three groups, called 'declensions': the second, the third-neuter or the fourth declension. Those in the 2nd have plurals in -i (dominus, domini); those in the 3rd-neuter have plurals in -a (vulnus, vulnera); and those in the 4th stay the same in the plural, although the U becomes a long vowel (exercitus, exercitus).

The first two nouns you mention are in the second declension, and the last is in the fourth. So in Latin the plurals would be 'hippopotami', 'cacti', 'census'.

In English both the forms 'hippopotami' and 'hippopotamuses' are used, and both 'cactuses' and 'cacti' are correct. 'Census' as a plural is not often found because it might be confused with the singular form. 'Censi' is incorrect. That leaves 'censuses' as the only available plural.

PS Latin words ending in -um all belong to the second-neuter declension, which forms plurals in -a: stadium, stadia; forum, fora. Normally in English, you have the choice whether to pluralize in -a or -ums: so both 'stadia' and 'stadiums' are correct.

PPS Not all words that end in -us are Latin! The word 'octopus' is Greek (via modern Latin), and its plural is not 'octopi' but 'octopuses'. In Greek the plural would be 'octopodes', but not in English.

As a general rule, I recommend pluralising words in -us in the English way (by adding -es), which is always correct, unless you are sure that the plural may also be -i or something else. That is the direction that English usage is taking in any case

Answer 2

Part of the problem is that English is not a direct descendent of any single language; It has roots from Latin, German, French andmany others.

As many languages have different rules for creating plurals, as well as for conjugation and tense, the rules in English are not consistent at all. The plural of mouse is mice, for instance, breaking your rule for animals above.

Going to a more pure language creates a better adherence to rules, but I'm not sure that any language is completely free from exceptions. English is just more replete with them.

Answer 3

It's the English Language so for every rule there's at least one exception! Actually "census" is not derived from a Latin word so the plural doesn't end in "i".

The basic rule is if the word is derived from Latin then the plural ends in "i" (like you'd know just by looking at it that it comes from Latin!). Examples:-
cactus cacti
hippopotamus hippopotami
octopus octopi
platypus platypi
rhinoceros rhinocerosi
uterus uteri
alumnus alumni
bacillum bacilli

Answer 4

The english language doesn't have clear rules. What might be true for one word isn't exactly true for another word in it's likeness! It's a messed up system that I had to go through when I had to learn english at the age of 9!

Answer 5

There are exceptions in all rules. In all laguages. That is why we find that all is depending on the ending of the words in question. In spanish, we know that a singular word changes in the root, by simply adding an "s" or "es".,i.eg: fósil-fósiles.

Answer 6

I've stopped trying to understand all the screwed up rules of the English language. Even more confusing is trying to teach someone who speaks another language, ahh.

Answer 7

That is the plural. How could you double the plural? "I went to the store and bought 256 containers of 'hummus'". "How many ------ can you eat?" doesn't work. Try, "How much hummus can you eat?" This is the same as guacamole and sour cream.

Answer 8

Because the English language is screwy.

Answer 9

remember when partrige said lexus had the singular lexi. what a pipe

Answer 10

because the english language is weird