An abacus is an ancient tool used for calculating that remains popular in some places even today. Some sort of counter (beads, beans, stones) is moved in a groove or on a wire to represent the different numbers in the equation.
Abacus is a Latin word from a Greek word abax, which meant "counting table." The original abaci were created in sand. The plural abacuses can also be used. In architecture, an abacus can also refer to a flat slab that sits on top of the broad part of a pillar or column (called the capital) to help support a beam (called an architrave) that rests across several pillars.