According to the E,z system of nomenclature, a set of sequence rules is used to assign priorities to the substituent groups on the double-bond carbons. Considering each doubly bonded carbon atom separately, the sequence rules are used to decide which of the two attached groups is higher in priority. If the higher-priority groups on each carbon are on the same side of the double bond the alkene is designated Z, for the German zusammen, meaning "together." If the higher-priority groups are on opposite sides, the alkene is designated E, for the German entgegen, meaning "opposite." (A simple way to remember which is which is to note that the groups are on "ze zame zide" in the Z isomer.)