assumption

The word “assumption” means something accepted as true without proof, or the act of accepting it as true. In plain terms, something taken to be true without being checked, or the act of taking on a role.

“Assumption” is pronounced uh-SUHM-shn (/əˈsʌm(p).ʃ(ə)n/ in IPA).

Here is “assumption” used in a sentence: “The whole plan rested on a false assumption.”

“Assumption” is a noun.

The word “assumption” comes from Latin. From Latin assumptio ("a taking up"), from assumere (see "assume"), plus the noun suffix "-ion".

“Assumption” is a fairly common word in modern English, usually learned at around the B2 level.

“Assumption” has 2 distinct senses listed in this dictionary. The most common is: something accepted as true without proof, or the act of accepting it as true.

An assumption is something accepted as true without proof, often unconsciously, as a starting point for reasoning. A presumption is usually a belief with somewhat more confidence or standing behind it — the law speaks of the presumption of innocence — and presumption can also mean overconfident, cheeky behavior. When there is no evidence either way, assumption is the safer word.

A hypothesis is a proposed explanation put forward deliberately so that it can be tested against evidence. An assumption is simply accepted as true without proof and often goes unexamined. In research, assumptions are the untested beliefs underlying a study, while the hypothesis is the claim the study is designed to test.

The standard collocation is 'make an assumption'; 'do an assumption' is not idiomatic English. Assumptions are also challenged, questioned, and based on things, and you can proceed 'on the assumption that' or 'under the assumption that' something is true. Both of those prepositional patterns are standard.