DictionaryassumptionUnproven belief
noun

assumption

uh-SUHMP-shun/əˈsʌmpʃn/

A belief accepted as true without proof.

He makes the assumption that the closed biscuit tin contains cookies.

An unopened biscuit tin is taken to contain biscuits because of its pictured contents: a man sets out a serving plate before checking inside, then discovers sewing supplies.
Etymology

The pieces form a noun of “taking to oneself,” hence acceptance or adoption. In reasoning, an assumption is a proposition taken as a premise or accepted as true without proof.

In context

Sean McDowell6:56
consciousness is a product of brain function. That was just an never proven uh assumption, never proven hypothesis. And um everybody thought it was true
Why Consciousness Continues Beyond Life: A Foremost Expert Speaks Out

More examples

  • That assumption turned out to be wrong.
  • We tested the assumptions behind the plan.
  • Her argument rested on a doubtful assumption.

Forms

assumption · assumptions

Similar words

presumption
Often suggests a belief adopted as a starting position.
supposition
Supposition emphasizes a tentative idea rather than an accepted starting belief.