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

Remember that no prescription is required — so no need to reach for your abacus to calculate a co-pay or rebate. — Ed Silverman, STAT, 10 June 2026

Workers mixed mortar and drove a scissor lift to the edge of a concrete plinth surmounted by four steel rods—supports for the Buddha, whose sandstone body would slide down them in four parts, like beads in an abacus. — Julian Lucas, New Yorker, 4 May 2026

What are you guys doing, using an abacus to calculate pre-money valuation? — Neil Senturia, San Diego Union-Tribune, 4 May 2026

Kids ages 5-12 can handle replica artifacts, such as an abacus, armor and lyre, and learn how professional archeologists make inferences. — Jennifer Day, Chicago Tribune, 19 Feb. 2026

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