Other forms: assumed, assuming, assumes
To assume is to take something as true without checking. I assumed you knew. Do not assume anything.
It is one of the most useful verbs in careful discussion, because naming an assumption is how you take an argument apart. The noun is assumption. There is a second and quite different sense meaning to take on: assume responsibility, assume control, assume office. That one is formal and common in writing about power. Note assuming that, which introduces a condition, and the old joke about what assuming does, which every English speaker has heard once too often.
1verbassumeTo accept something as true without proof.
“I assumed the shop would be open.”
2verbroleTo take on a role or responsibility.
“She assumed control of the department in March.”
3verbappearanceTo take on an appearance that is not real.
“He travelled under an assumed name.”
Too few real examples of this word to estimate which sense is commonest.
assume is a way of taking as true.
Also accepted in games: presume
Latin assumere is ad-, to, plus sumere, to take — the same verb behind consume, resume and presume. Both English senses are taking: taking something as true, and taking something on.
Proto-Indo-European
*h₁em-
Latin
assūmō — accept, take
English, today
assume
Built from
From Latin assūmō (“accept, take”), from ad- (“to, towards, at”) + sūmō (“take up, assume”).
Etymology from Wiktionary, CC BY-SA