▁with ▁prefix es . ▁This ▁relationship ▁is ▁compatible ▁with ▁the ▁decimal ▁system ▁of ▁numbers ▁and ▁it ▁cont ributes ▁greatly ▁to ▁the ▁convenience ▁of ▁metric ▁units . ▁ ▁In ▁the ▁early ▁metric ▁system ▁there ▁were ▁two ▁base ▁units , ▁the ▁met re ▁for ▁length ▁and ▁the ▁gram ▁for ▁mass . ▁The ▁other ▁units ▁of ▁length ▁and ▁mass , ▁and ▁all ▁units ▁of ▁area , ▁volume , ▁and ▁derived ▁units ▁such ▁as ▁density ▁were ▁derived ▁from ▁these ▁two ▁base ▁units . ▁ ▁Mes ures ▁us u elles ▁( F rench ▁for ▁custom ary ▁measurements ) ▁were ▁a ▁system ▁of ▁measurement ▁introduced ▁as ▁a ▁comprom ise ▁between ▁the ▁metric ▁system ▁and ▁traditional ▁measurements . ▁It ▁was ▁used ▁in ▁France ▁from ▁ 1 8 1 2 ▁to ▁ 1 8 3 9 . ▁ ▁A ▁number ▁of ▁variations ▁on ▁the ▁metric ▁system ▁have ▁been ▁in ▁use . ▁These ▁include ▁gravit ational ▁systems , ▁the ▁cent imet re – gram – second ▁systems ▁( c gs ) ▁useful ▁in ▁science , ▁the ▁met re – ton ne – second ▁system ▁( m ts ) ▁once ▁used ▁in ▁the ▁USS R ▁and ▁the ▁met re – kil ogram – second ▁system ▁( m ks ). ▁In ▁some ▁engineering ▁fields , ▁like ▁computer - a ided ▁design , ▁millimeter – gram – second ▁( mm gs ) ▁is ▁also ▁used . ▁ ▁The ▁current ▁international ▁standard ▁metric ▁system ▁is ▁the ▁International ▁System ▁of ▁Units ▁( S yst ème ▁international ▁d ' unit és ▁or ▁SI ) ▁It ▁is ▁an ▁m