abacus
noun /ˈæbəkəs/
  /ˈæbəkəs/
(plural abacuses 
 /ˈæbəkəsɪz/
  /ˈæbəkəsɪz/
)- a frame with small balls that slide along wires. It is used as a tool or toy for counting.Word Originlate Middle English (denoting a board strewn with sand on which to draw figures): from Latin, from Greek abax, abak- ‘slab, drawing board’, of Semitic origin; probably related to Hebrew 'āb̲āq ‘dust’.