/ əˈsʌmpʃn; NAmE / noun
1.
[ C ] a belief or feeling that sth is true or that sth will happen, although there is no proof :
an underlying / implicit assumption
We need to challenge some of the basic assumptions of Western philosophy.
We are working on the assumption that everyone invited will turn up.
It was impossible to make assumptions about people's reactions.
His actions were based on a false assumption.
2.
[ C , U ] assumption of sth ( formal ) the act of taking or beginning to have power or responsibility :
their assumption of power / control
••
WORD ORIGIN
Middle English : from Old French asompsion or Latin assumptio(n-) , from the verb assumere , from ad- towards + sumere take.