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An abacus is a counting frame: a wooden or plastic frame with rods, and small beads that slide along the rods. You move the beads to add, , and do other sums.
An abacus算盤is a counting frame是一種計數用的架子：a wooden or plastic frame with rods木頭或塑膠做的框架上裝著一根根的軸，and small beads that slide along the rods還有可以沿軸滑動的小珠子。You move the beads你移動珠子，to add, subtract, and do other sums就能做加法、減法和其他運算。
Before cheap electronic calculators, many shops and schools in East Asia used one every day. Each rod stands for a place value — ones, tens, hundreds, and so on — so the tool is a physical place-value chart, not only a toy, though it can look like one.
Before cheap electronic calculators在便宜的電子計算機出現以前，many shops and schools in East Asia東亞很多商店和學校，used one every day每天都會用它。Each rod stands for a place value每一根軸代表一個位數——ones, tens, hundreds, and so on個位、十位、百位等等——so the tool is a physical place-value chart所以這個工具其實是實體的位值表，not only a toy不只是個玩具，though it can look like one雖然它看起來可能像玩具。
Some children still learn bead arithmetic as a skill and a mental exercise.
Some children still learn bead arithmetic現在還是有小孩在學珠算，as a skill and a mental exercise把它當成一種技能和心算的練習。
The usual plural in English is abacuses; the Latin plural abaci still appears in formal writing.
The usual plural in English英文裡常見的複數is abacuses是abacuses；the Latin plural abaci拉丁文的複數abaci，still appears in formal writing還會出現在正式的寫作裡。
You meet the word in maths history, in classrooms, and sometimes as a metaphor for someone very quick with numbers.
You meet the word你會遇到這個字in maths history在數學史裡、in classrooms教室裡，and sometimes as a metaphor有時候也當作比喻，for someone very quick with numbers用來形容一個對數字反應很快的人。
組成From Late Middle English, from Latin abacus, from Ancient Greek ἄβαξ (ábax), a slab or counting board. English borrowed the Latin word; the Latin-style plural abaci is still used in careful writing.
原始詞典資料4 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
abacusnoun/ˈæb.ə.kəs/
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obsoletehistoricalA 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, [...]
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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.
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architectureThe 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.
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historicalA 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.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。