abacus

noun

Etymology: From Late Middle English abacus, abagus, agabus (“abacus; art of counting with an abacus”), from Latin abacus, abax (“sideboard or table with a slab at the top; slab at the top of a column; counting board, sand table; board for playing games”) (compare Late Latin abacus (“art of arithmetic”)), from Ancient Greek ἄβαξ (ábax, “slab, counting board; board covered with sand for drawing; plate; dice-board”). Doublet of abaque and abac. The plural form abaci is reinforced from Latin abacī.

1. A table or tray scattered with sand which was used for calculating or drawing.

   “He [Gerebertus] was þe firste þat took abacus of Sarsyns, and ȝaf rules þerynne, þat mowe unneþe be understonde of þe kunnyngeste men of þe craft, þe whiche craftes men beþ cleped abaciste. Marianus. Abacus is a table wiþ þhe whiche schappes be portrayed and i-peynt in powdre, and abacus is a craft of geometrie.”

   “[H]e set fondly and furiously to work upon [Thomas] Simpson's Euclid, [...] The smooth grassy sod answered all the purposes of the abacus, and the cows generously supplied him in a substitute for sand. Spreading and smoothing that substitute with his bear foot, he engraved upon it with his finger the mystic lines and letters; and, with book in hand, proceeded to establish the elementary principles of geometry, [...]”

2. 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.

   “I’ve heard merchants still use an abacus for adding things up in China.”

   “Before leaving the question of early arithmetic I should mention that for practical purposes the almost universal use of the abacus or swan-pan rendered it easy to add or subtract, or even to multiply and divide, without any knowledge of theoretical mathematics. [...] [I]t will be sufficient here to say that they afford a concrete way of representing a number in the decimal scale, and enable the results of addition and subtraction to be obtained by a merely mechanical process.”

3. 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.

   “The only mouldings uſed, both by the Saxon and Norman architects, were the torus, the ſcotia or reverſed torus, the cavetto or hollow moulding, and a kind of chamfered faſcia, which latter was generally uſed for impoſts or abacuſes to their capitals.”

   “At Amiens, the square form of the abaci, and the volutes of the capitals, afford a decisive proof that the Norman fashion had not yet been superseded. On the other hand, at Salisbury, the abaci are mostly round, and where foliage is used in the capitals, their graceful and luxurious design clearly shews an advancement in that department of the art.”

4. A board, tray, or table, divided into perforated compartments for holding bottles, cups, or the like; a kind of buffet, cupboard, or sideboard.

   “ABACUS, among the ancients, was a kind of cupboard or buffet. Livy, deſcribing the luxury into which the Romans degenerated after the conqueſt of Aſia, ſays they had their abaci, beds, &c. plated over with gold.”

   “The plate and nicknacks, always found in elegant Roman houses, were displayed on small one or three legged tables (trapezophoron), the slabs of which (abacus, a word which, like trapezophoron, is sometimes used for the whole table) had raised edges round them: several richly ornamented specimens of such tables have been found at Pompeii. Fig. 446 shows a small abacus resting on three marble legs, which has been found in the house of the "Little Mosaic-Fountain" at Pompeii.”