Inflected forms: pl. ab·a·cus·es or ab·a·ci ( b-s, -bk) 1. A manual computing device consisting of a frame holding parallel rods strung with movable counters. 2.Architecture A slab on the top of the capital of a column.
ETYMOLOGY:
Middle English, from Latin, from Greek abax, abak-, counting board, perhaps from Hebrew ’bq, dust. See bq in Appendix II.
WORD HISTORY:
The adjective dusty, with its connotations of disuse and age, might seem an appropriate word to describe the abacus, since this counting device was used for solving arithmetical problems in the days before calculators and computers. Originally the abacus was, in fact, dusty. The source of our word abacus, the Greek word abax, probably comes from Hebrew ’bq, “dust,” although the details of transmission are obscure. In postbiblical usage ’bq meant “sand used as a writing surface.” The Greek word abax has as one of its senses “a board sprinkled with sand or dust for drawing geometric diagrams.” This board is a relative of the abacus with movable counters strung on rods that is familiar to us. The first use of the word abacus, recorded in Middle English in a work written before 1387, refers to a sand-board abacus used by the Arabs. The difference in form between the Middle English word abacus and its Greek source abax is explained by the fact that Middle English borrowed Latin abacus, which came from the Greek genitive form (abakos) of abax.
b
-k
, 
b
bq in Appendix II.
