Is there any difference in the meaning of these words? Which one of them is used the most in everyday conversation?

In my vocabulary for both words I've found essentially the same meaning: "difficult to do and needing a lot of effort".

4 Answers 4


To me the difference lies in their origins.

"Onerous" means "burdensome" - not necessarily difficult or physically hard, but unwelcome and required of one. (Maybe unpleasant, or just taking time away from other things)

"Arduous" means "requiring effort".

These may overlap in many cases, but to me are quite different.


I would say that "onerous" implies more of a mental difficulty, while "arduous" is a physical difficulty.


That contract placed an onerous duty on me because I had to tabulate the reports every day.
Moving the furniture upstairs was an arduous labour.

However, the distinction is usually fairly transparent in context, so you can generally use either word without loss of meaning.

  • 5
    I don't think this is the primary distinction - something can be mentally challenging but not burdensome, and then "onerous" would be a bad description. Onerous implies unwelcome as Colin Fine said below - and this unwelcome-ness is "mental" in the sense of it being psychologically unappealing Nov 25, 2010 at 12:29

Onerous means "burdensome", related to onus "burden". Arduous means "difficult" and derives from the Latin arduus "high, steep". So while there is certainly some overlap, the words are not perfect synonyms. For example, it would be appropriate to refer to:

...the onerous backpack on our arduous climb...

or, in a figurative sense,

...the onerous secret in our arduous relationship...

It would make less sense to talk about "the arduous backpack on our onerous climb" or "the arduous secret in our onerous relationship".

  • The original meaning of words on being adopted into the lexicon doesn't dictate their present-day meaning. I'd agree though that there is a continuing informing in this case. But isn't this a restatement of Colin's answer? Jun 2, 2023 at 11:00

Look at the root words. Onus is an obligation. Ardor is passion. Mountain climbing is arduous. It's hard work but you enjoy it. Changing a baby's diapers is onerous.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.