abacus

noun

aba·​cus ˈa-bə-kəs  ə-ˈba- 

plural abaci ˈa-bə-ˌsī 

-ˌkē;

ə-ˈba-ˌkī  or abacuses

1

: an instrument for performing calculations by sliding counters along rods or in grooves

2

: a slab that forms the uppermost member or division of the capital of a column

Illustration of abacus

• abacus 1

Did you know?

Probably of Babylonian origin, an abacus is a calculating instrument that uses beads that slide along a series of wires or rods set in a frame to represent the decimal places. It is the ancestor of the modern digital calculator. Used by merchants in the Middle Ages throughout Europe and the Arabic world, it was gradually replaced by arithmetic based on Hindu-Arabic numerals. Though rarely used in Europe past the 18th century, it is still used in the Middle East, China, and Japan.

Examples of abacus in a Sentence

Recent Examples on the Web

Its surface shimmers with a girlie patina of iridescent pink and turns stacks of abacus beads into bangle bracelets. —Deborah Solomon, New York Times, 13 Feb. 2025

This compact busy board is for children 12 months and older and includes a maze, abacus, peek-a-boo door with a surprise mirror inside, gears, a light switch toggle, and a three-prong plug. —Chaunie Brusie, Rn, Parents, 7 Feb. 2025

All forms of classical computing, whether an abacus, a personal laptop, or a high-performance cluster of machines in a national security facility, follow what scholars call Boolean logic. —Charina Chou, Foreign Affairs, 7 Jan. 2025

Tallied with a fancy algorithm or an abacus, the revenue disparity is substantial: $16.3 million per year for each Bay Area school, on average. —Jon Wilner, The Mercury News, 1 Aug. 2024

Word History

Etymology

Latin, from Greek abak-, abax, literally, slab

First Known Use

14th century, in the meaning defined at sense 1

Kids Definition

abacus

noun

aba·​cus ˈab-ə-kəs  ə-ˈbak-əs 

plural abaci ˈab-ə-sī  -ˌkē 

ə-ˈbak-ˌī

or abacuses

: an instrument for making calculations by sliding counters along rods or in grooves