Abacus

ab·a·cus [ab-uh-kuhs] noun

1. a calculator that performs arithmetic functions by manually sliding counters on rods or in grooves.

2. a tablet placed horizontally on top of the capital of a column as an aid in supporting the architrave.

3. an ancient diagram showing the structure and disposition of the keys of an instrument.

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

Origin
[Middle English, Latin, Greek: abax, abak- (counting board), perhaps from a Semitic source akin to Hebrew ’ābāq (dust) ] [[Category:A]]