Abacus (noun)

1. A device used for counting and calculation, typically consisting of a frame with beads or disks that can be moved along rods or grooves.
2. A mental counting or calculation system.

Origin:

From the latin word "abacus" meaning "board with pebbles for calculating" or "calculating table" , ultimately from the greek word "abax" meaning "board covered with dust". the word was first used in english in the 15th century.

Examples:

1. The abacus is an ancient counting tool that was used in many cultures.
2. The abacus is still used in some parts of the world as a primary calculating tool.
3. The abacus was used to teach basic arithmetic to children.
4. The abacus was an important tool for merchants and traders.
5. The abacus helped the man to perform complex calculations quickly.