▁weight ▁of ▁water ▁in ▁a ▁k eg ▁of ▁specific ▁size , ▁perhaps ▁itself ▁defined ▁in ▁hands ▁and ▁kn uck les . ▁The ▁un ifying ▁characteristic ▁is ▁that ▁there ▁was ▁some ▁definition ▁based ▁on ▁some ▁standard . ▁Event ually ▁cub its ▁and ▁str ides ▁gave ▁way ▁to ▁" custom ary ▁units " ▁to ▁meet ▁the ▁needs ▁of ▁mer ch ants ▁and ▁scient ists . ▁ ▁In ▁the ▁metric ▁system ▁and ▁other ▁recent ▁systems , ▁a ▁single ▁basic ▁unit ▁is ▁used ▁for ▁each ▁base ▁quantity . ▁O ften ▁secondary ▁units ▁( multi ples ▁and ▁sub multi ples ) ▁are ▁derived ▁from ▁the ▁basic ▁units ▁by ▁multip lying ▁by ▁powers ▁of ▁ten , ▁i . e . ▁by ▁simply ▁moving ▁the ▁decimal ▁point . ▁Thus ▁the ▁basic ▁metric ▁unit ▁of ▁length ▁is ▁the ▁met re ; ▁a ▁distance ▁of ▁ 1   m ▁is ▁ 1 , 0 0 0   mill imet res , ▁or ▁ 0 . 0 0 1   kil omet res . ▁ ▁Current ▁practice ▁ ▁Met ric ation ▁is ▁complete ▁or ▁nearly ▁complete ▁in ▁almost ▁all ▁countries . ▁US ▁custom ary ▁units ▁are ▁heavily ▁used ▁in ▁the ▁United ▁States ▁and ▁to ▁some ▁degree ▁in ▁Liber ia . ▁Trad itional ▁Bur m ese ▁units ▁of ▁measurement ▁are ▁used ▁in ▁Bur ma . ▁U . S . ▁units ▁are ▁used ▁in ▁limited ▁context s ▁in ▁Canada ▁due ▁to ▁the ▁large ▁volume ▁of ▁trade ; ▁there ▁is ▁also ▁considerable ▁use ▁of ▁Imperial ▁weights ▁and ▁measures , ▁despite ▁de ▁j ure ▁Canadian ▁conversion ▁to