Definition of assumption noun from the Oxford Advanced American Dictionary



1 [countable] a belief or feeling that something is true or that something will happen, although there is no proofan underlying/implicit assumptionWe need to challenge some of the basic assumptions of Western philosophy.We are working on the assumption that everyone invited will show up.It was impossible to make assumptions about people's reactions.His actions were based on a false assumption.She arrived at college with a whole set of assumptions inherited from her family.2 [countable, uncountable] assumption of something (formal) the act of taking or beginning to have power or responsibilitytheir assumption of power/controlthe assumption of responsibility by the government for the disaster