A Japanese Abacus, with 5 beads in 15 rows. Abacus comes from the Greek word 'abax' which means calculating board or calculating table. Japanese Abacus is characterized by having diamond shaped beads, 1 in the lower section and 4 in the upper. An abacus is used for addition, subtraction, multiplication, and division, as well as fractions and square root. In this instrument, the frame divider and beads are made of hard plastic; the runners are made of high quality bamboo.