< But this doesn't explain why some units are not common even in scientifi < fields. Like the millifarad, for example. This is because that is an odd size 1000mF (10^-6) is rather uncommon when standard values and notation came about. Back then a 50mF cap was a large value! It was the advent of transistor circuits and their lower voltage power supplies that 1000mF were common. Then again we see caps now in the full Farad sizes. Then again from a womans point of view, it may be that 1400mm sounds bigger than 5 and a half inches. ;) Allison