Plural of “syllabus”

The plural of syllabus is syllabi (some dictionaries also accept syllabuses).

Why

"Syllabus" actually has a murky, disputed etymology: it likely originated from a medieval scribal misreading of a Latin manuscript, possibly confusing a form of the Greek word for a book label or table of contents, rather than descending cleanly from a genuine classical Latin word the way "cactus" or "radius" do — despite that shaky origin, it was assigned a Latin-style -us/-i plural once it entered English academic vocabulary.

Because its Latin pedigree is genuinely questionable rather than solid, some usage commentators have specifically argued "syllabuses" is actually the more historically defensible plural, even though "syllabi" remains extremely common in academic speech purely by analogy with words like "alumnus/alumni" and "radius/radii" that are unambiguously Latin. Interestingly, the word's disputed origin hasn't stopped it from becoming one of the most frequently pluralized academic nouns students actually encounter, since nearly every college course requires one, meaning the syllabus/syllabi debate is one of the more practically relevant Latin-plural questions for the average student, even though its classical pedigree is genuinely shakier than words like "alumnus" or "radius." Some etymologists have also proposed alternative, equally uncertain origins tracing the word to a different Greek term for a parchment label, underscoring just how unsettled the word's history really is compared to the confidently documented origins of most other words on this list.

Usage note

Both plurals appear constantly in university and school settings without either reading as wrong: professors and administrators say "syllabi" about as often as "syllabuses," and most institutional style guides simply don't take a firm position, unlike some other -us words where one form clearly dominates in professional use.

Online course-management platforms and academic style guides increasingly default to "syllabi" in their own interface language, which has likely reinforced the form's dominance in higher education specifically, even as general dictionaries continue to list "syllabuses" as an equally standard, and arguably more historically justified, alternative. Learning management software used by most universities today, such as course-management platforms that host digital syllabi, has effectively standardized "syllabi" as the default plural in higher education technology, likely accelerating its dominance in academic settings even as general dictionaries continue to present "syllabuses" as an equally valid, and arguably better justified, alternative.

Common real mistakes

There's no true error between the two forms, but it's worth knowing that "syllabi" here is something of a borrowed convention rather than a strict inheritance from classical Latin — treating it as etymologically mandatory, the way "cacti" genuinely is for "cactus," overstates how settled the word's Latin credentials actually are. A further subtlety some writers miss: treating "syllabi" as if it demanded the same strict register rules as unambiguously Latin words like "alumni" overstates the case, since "syllabuses" carries no real stigma even in fairly formal academic prose, unlike using a regularized plural for a word with a truly solid classical pedigree.

The wider pattern

"Syllabus" is often grouped with genuinely Latin -us/-i nouns like "radius/radii," "alumnus/alumni," and "stimulus/stimuli," but its own etymology is murkier than any of those, making its Latin-style plural more a matter of adopted academic convention than a strict inheritance.

Examples

• The professor handed out syllabi on the first day of class.
• Every course syllabus outlined the grading policy in detail.
• The department reviewed all its syllabuses before the semester began.
• Students compared syllabi to see which class had less homework.
• The updated syllabus included two additional required readings.
• Faculty submitted their syllabuses for approval each term.
• Several syllabi listed the same required textbook.
• The new syllabus reflected feedback from student evaluations.
• Instructors are required to post their syllabi online.
• Two different syllabuses covered nearly identical material.
• The registrar's office archives syllabi from every course offered in the past decade.
• New instructors are given sample syllabuses to use as a starting template.