Plural of abacus

irregular plural

The plural of abacus is abaci or abacuses.

Forms of abacus

Singular	abacus /ˈæb.ə.kəs/
Plural	abaci /ˈæbəkaɪ/ abacuses /ˈæbə.kəsɪz/
Countable	countable

The computer is but another vehicle to employ in helping people learn, a cousin of books, films, blackboards, chalk, gerbils, abacuses.1974, Theodore R[yland] Sizer, “Foreword”, in Allan B. Ellis, The Use & Misuse of Computers in Education, New York, N.Y.: McGraw-Hill Book...
Before Pythagoras it was necessary to see the thing before counting it, like children who learn on abacuses, with balls sliding along rods: children learn to add and subtract by sliding stones.2001, Augusto Boal, “The Impossible Return and the Strangeness of the Familiar”, in Adrian Jackson, Candida Blaker, transl., Hamlet and the...

noun A table or tray scattered with sand which was used for calculating or drawing.
noun A device used for performing arithmetical calculations; (rare) a table on which loose counters are placed, or (more commonly) an instrument with beads sliding on rods, or counters in grooves, with one row of beads or counters representing units, the next tens, etc.
noun The uppermost portion of the capital of a column immediately under the architrave, in some cases a flat oblong or square slab, in others more decorated.

What is the plural of abacus?: The plural of abacus is abaci or abacuses.
Which is correct, abaci or abacuses?: Both are used. abaci is the more common of the two in English writing.
Is abacus countable?: Abacus is a countable noun.

Adapted from Wiktionary: abacus (page history and authors) and the entries of its forms. Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws left out forms marked obsolete, archaic, rare or dialectal and added the examples. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

Cite this page: “Plural of abacus.” Word.ws, https://word.ws/plural/abacus. Based on Wiktionary, CC BY-SA 4.0.