ap ‧ por ‧ tion /əˈpɔːʃ ə n $ -ɔːr-/ BrE AmE verb [transitive] formal
[ Date: 1500-1600 ; Language: French ; Origin: apportionner , from portionner 'to portion' ]
to decide how something should be shared among various people:
It’s not easy to apportion blame (=say who deserves to be blamed) when a marriage breaks up.
apportion among/between
Court costs were equally apportioned between them.
—apportionment noun [uncountable and countable]