What is the plural of ‘syllabus’?

If you’re like me, at the start of every semester you always wonder why the plural of syllabus is syllabi.

Or why the plural of auditorium is auditoria.
Or why the plural of analysis is analyses.
Or (if you’re a math major) why the plural of formula is formulae.

Or (if you’re a statistics major) why the word “data” is actually plural, and its singular use is “datum”, which nobody uses anyway.

OK, so maybe you’re not as nerdy as I am. Or, equally likely, I myself became much more of a nerd after taking Latin 101 last year. Because when I did, everything clicked! It turns out that all these words are Latin in origin and, as such, so are their plurals.

Check out the table above. When a singular noun (i.e. nominative) ends in -us, like syllabus, it’s masculine and its plural ends in -i. When it ends in -a, like formula, it’s feminine and its plural ends in -ae. And when it ends in -um, like auditorium, it’s neuter and its plural ends in -a. Another possibility not shown above is the third declension, when a word ends in -is (like analysis) in which case it’s plural is formed by changing this to -es (i.e. analyses).

The reason I bring this up is in part due to our recent discussions about academia (itself a Latin word!) and the writing expectations that go along with it. While most academics likely won’t get bent out of shape over saying “formulas” instead of “formulae”, knowledge of these plurals can still be very useful, even in informal writing. However, this knowledge can also be dangerous–it means having to stifle a cringe whenever someone messes up…and, of course, being labeled a nerd when you point this out. I have my Latin 101 prof to thank for that!


1) What is the plural of census?

2) What is the plural of stadium?

3) What is the singular of parentheses?

2 thoughts to “What is the plural of ‘syllabus’?”

  1. I have never taken Latin before but I have taken Spanish and Italian. I never knew that scholars get mad over what many people never even think twice about!


    …those could very well be wrong haha!

  2. Great job, Alexis! The only one you missed was the second one, which I believe is a neuter noun and so should be stadia in the plural. It’s so tempting to just add that -s at the end, isn’t it? I also think it’s really counter-intuitive to have all these plurals that don’t end in -s.

    Does Italian have anything similar? From my high school studies, I don’t believe Spanish does.

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