What does the word onus mean? According to Collins English Dictionary and the American Heritage Unabridged Dictionary of the English Language, the word onus is a noun that means a duty or responsibility. This is often used in the phrase “the onus is on” which means a responsibility is on a person or thing to do something.

the responsibility or duty to do something: The onus is on the administration to come up with a balanced budget. (Definition of onus from the Cambridge Academic Content Dictionary © Cambridge University Press)

formal us / ˈoʊ.nəs / uk / ˈəʊ.nəs / the responsibility or duty to do something: [ + to infinitive ] The onus is on the landlord to ensure that the property is habitable. We are trying to shift the onus for passenger safety onto the government.

1. A difficult or disagreeable responsibility or necessity; a burden or obligation. 2. Responsibility for an error or fault; blame: Each side wants to avoid the onus of having started the disagreement.

noun /ˈəʊnəs/ /ˈəʊnəs/ (usually the onus) [singular] (formal) the responsibility for something The onus is on employers to follow health and safety laws. The onus of proof lies with the prosecution. The report puts the onus of children’s early education firmly on the parents.