Take the noun, onus, as a formal word for responsibility or obligation. If your teacher assigns onus as a vocabulary word, it puts the onus on you to find out what it means.

Onus is a formal or sophisticated way to say "responsibility" or "duty." It sounds a little like the unrelated word owner, so think about the person with onus as owner of the responsibility. If the onus is on you to organize a fund raiser, you have to set the whole thing up. Have you ever heard the legal term onus probandi? It means the burden of proof, which requires the accuser to prove the case against the accused.

Definitions of onus

n an onerous or difficult concern

burden, encumbrance, incumbrance, load
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dead weight
an oppressive encumbrance
a burden (figuratively in the form of a bundle)
an uncalled-for burden
something unpleasant or offensive that must be tolerated or endured
Type of:
concern, headache, vexation, worry
something or someone that causes anxiety; a source of unhappiness

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