assumption (n.)

c. 1300, "the reception, uncorrupted, of the Virgin Mary into Heaven" (also the Aug. 15 Church festival commemorating this, Feast of the Assumption), from Old French assumpcion, asumpsion (13c.) and directly from Latin assumptionem (nominative assumptio) "a taking up, receiving, acceptance, adoption," noun of action from past-participle stem of assumere "take up, take to oneself" (see assume).

Meaning "minor premise of a syllogism" is late 14c. Meaning "appropriation of a right or possession" is mid-15c. in English, from a Latin use (Cicero). Meaning "action of taking for oneself" is recorded from 1580s; that of "something taken for granted" is from 1620s.

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Definitions of assumption
assumption (n.)
a statement that is assumed to be true and from which a conclusion can be drawn;
on the assumption that he has been injured we can infer that he will not play
Synonyms: premise / premiss
assumption (n.)
a hypothesis that is taken for granted;
any society is built upon certain assumptions
Synonyms: supposition / supposal
assumption (n.)
the act of taking possession of or power over something;
he acquired all the company's assets for ten million dollars and the assumption of the company's debts
his assumption of office coincided with the trouble in Cuba
the Nazi assumption of power in 1934
Synonyms: laying claim
assumption (n.)
audacious (even arrogant) behavior that you have no right to;
Synonyms: presumption / presumptuousness / effrontery
assumption (n.)
the act of assuming or taking for granted;
your assumption that I would agree was unwarranted
Assumption (n.)
celebration in the Roman Catholic Church of the Virgin Mary's being taken up into heaven when her earthly life ended; corresponds to the Dormition in the Eastern Orthodox Church;
Synonyms: Assumption of Mary / August "
Assumption (n.)
(Christianity) the taking up of the body and soul of the Virgin Mary when her earthly life had ended;