noun, plural o·nus·es.

a difficult or disagreeable obligation, task, burden, etc.
burden of proof.Compare onus probandi.
blame or responsibility.

Origin of onus

1630–40; < Latin: load, burden

Synonyms for onus

onus probandi

[oh-noo s proh-bahn-dee; English oh-nuh s proh-ban-dahy, -dee]

noun Latin.

the burden of proof.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for onus

Contemporary Examples of onus

Historical Examples of onus

  • It threw upon the Senate the onus of repairing the defects of the bill.

  • Any tyro in the logics will tell thee that the onus of proving lies with the accuser.

  • At all events the onus of proof rests with those who assert it is imponderable.

    Aether and Gravitation

    William George Hooper

  • Let it be understood by such as are aware of what has been, that I bear the onus of the rupture.


    Charlotte M. Yonge

  • The onus of speech seemed to rest with him, and he accepted it.

    The Yellow House

    E. Phillips Oppenheim

British Dictionary definitions for onus


noun plural onuses

a responsibility, task, or burden

Word Origin for onus

C17: from Latin: burden

onus probandi


law the Latin phrase for burden of proof
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for onus

1640s, from Latin onus "load, burden," figuratively "tax, expense; trouble, difficulty," from PIE *en-es- "burden" (cf. Sanskrit anah "cart, wagon"). Hence legal Latin onus probandi (1722), literally "burden of proving."

Online Etymology Dictionary, © 2010 Douglas Harper