In the metric system units of volume, as well as units of area, were formed on the basis of units of length measurement, proceeding from the fact that the volume of cube is equal to its edge in a power of 3. Thus, the metric units of volume are units of length measurement with the prefix "cubic", except of liter. This rule also applies to UK volume units based on units of length. At the same time, United Kingdom and USA use their own volume measurement systems, where each unit represents a historically developed measure. These units, unlike metric ones, are interconnected by rather complex relations and proportions. Similar to this system in Russia there is an Obsolete Russian measure of liquids, saved for today only in speech. In addition to conventional volume measurement units, in the cooking of all countries are used measures of spoon and glass, just to simplify the recipes.