I once taught at a small technical college in New York City. When teaching at a technical college, much to many adjuncts’ chagrin, you have to write all your own material, from the grading rubrics to the final exams. This also means a lot of administrative work, including copying, printing, paper-clipping, and the like.
The copy machine at our college happened to be across from the provost’s office, and, one evening, like many evenings, I stood before it spacing out and hoping the darned thing wouldn’t jam. Then the provost walked by and greeted me.
“Just copying syllabuses for my 8 p.m. English class,” I said, in an effort to make small talk. The provost was 5’11” and quite intimidating.
“You mean syllabi,” she said, before returning to her office.
I was dumbfounded. I knew I’d read that “syllabuses” was perfectly acceptable in a oft-referenced style guide, but how could I contradict the provost of my school? She was one step down from the school president, who was one step down from the owner. So I kept my mouth shut. Until now.
Say it with me: syllabuses! Feels good, doesn’t it? Yes, “cactuses”can be used as the plural of “cactus” and “syllabuses” as the plural of “syllabus.” So, the next time someone looks at you askew or corrects you, tell them it’s 100% O.K. unless you’re writing an extremely formal paper.
Merriam-Webster agrees with me. So does the AP Style Guide and Grammarist.com. So there.
Exceptions? There are a few, including “alumni.” It would look and sound pretty silly to forgo the Latin ending here and say “alumneses.” Plus, anyone who tries to single-handedly advance the English language usually looks like a douche. See this post for more on Latin endings in English.