When expressing some physical quantities, we may have to express them in very large numbers or very small numbers, such as the power generated from a power station (a very large number), or the time between two nuclear events (a very small number). Therefore, it was found appropriate to use prefixes to express these numbers. When expressing some physical quantities, we may have to express them in very large numbers or very small numbers, such as the power generated from a power station (a very large number), or the time between two nuclear events (a very small number).