onerous

adjective

oner·​ous ˈä-nə-rəs  ˈō- 

1

: involving, imposing, or constituting a burden : troublesome

an onerous task

onerous regulations

an onerous mortgage

2

: having legal obligations that outweigh the advantages

an onerous contract

onerously adverb

onerousness noun

Did you know?

What is the Difference Between onerous, burdensome, oppressive?

Not to go too heavy on the etymology, but the story behind onerous is at once straightforward and, dare we say, poetic. But perhaps that’s putting the cart before the horse. Onerous rolled into the English language during the 14th century, via Middle French, from the Latin adjective onerosus, "burdensome." That word, in turn, was hitched to the noun onus, meaning "burden" (source too of our word onus, which usually refers to a burden or responsibility). Onus shares an ancient root with the Sanskrit word anas, meaning "cart." So although onerous stresses a sense of laboriousness and often figurative heaviness (especially because something is distasteful, e.g. "the onerous task of cleaning up the mess"), it has a deep connection with a literal weight borne by a person, horse, or other beast of burden.

Synonyms

• bitter
• brutal
• burdensome
• cruel
• excruciating
• grievous
• grim
• hard
• hardhanded
• harsh
• heavy
• inhuman
• murderous
• oppressive
• rough
• rugged
• searing
• severe
• stiff
• tough
• trying

Choose the Right Synonym for onerous

onerous, burdensome, oppressive, exacting mean imposing hardship.

onerous stresses being laborious and heavy especially because distasteful.

the onerous task of cleaning up the mess

burdensome suggests causing mental as well as physical strain.

burdensome responsibilities

oppressive implies extreme harshness or severity in what is imposed.

the oppressive tyranny of a police state

exacting implies rigor or sternness rather than tyranny or injustice in the demands made or in the one demanding.

an exacting employer

Examples of onerous in a Sentence

Then everyone was asked, how fairly did you act?, from "extremely unfairly" (1) to "extremely fairly" (7). Next they watched someone else make the assignments, and judged that person's ethics. Selflessness was a virtual no-show: 87 out of 94 people opted for the easy task and gave the next guy the onerous one. —Sharon Begley, Newsweek, 23 June 2008

The first hitch occurred when the state education department took a full six months after the new law was adopted to issue 12 pages of onerous rules and regulations governing Arkansas charter schools. —Wendy Cole, Time, 10 June 2000

Environmentalism poses stark issues of survival, for humankind and for all those other tribes of creatures over which we have exercised our onerous dominion. —Marilynne Robinson, The Death of Adam, 1998

Rap tested well, but early on the promoters said they wouldn't be booking any gangsta rap, a move at least partly designed to calm security concerns during the onerous process of complying with the strict mass-gathering laws enacted in the wake of the 1969 festival. —John Milward, Rolling Stone, 11 Aug. 1994

The government imposed onerous taxes on imports.

had the onerous and stressful job of notifying the families of soldiers killed in action

Recent Examples on the Web

But then the costs rise, the subscription tiers multiply and the terms and conditions become increasingly onerous. —Alexis Soloski, New York Times, 10 Apr. 2025

What Britain’s small businesses are facing, though, is a huge amount of very unwelcome uncertainty, which could affect their ability to trade with the U.S. even if the tariffs themselves are not seen as too onerous. —Trevor Clawson, Forbes.com, 7 Apr. 2025

Those packages are numerous and onerous for customs officials to scan for tariffs. —David Goldman, CNN, 24 Mar. 2025

But the approach was slow, onerous and fundamentally ineffective. —Nolan Hout, Forbes, 24 Mar. 2025

Word History

Etymology

Middle English, from Middle French honereus, from Latin onerosus, from oner-, onus burden; akin to Sanskrit anas cart

First Known Use

14th century, in the meaning defined at sense 1

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Kids Definition

onerous

adjective

oner·​ous ˈän-ə-rəs  ˈō-nə- 

: being difficult and unpleasant to do or to deal with

an onerous task

onerously adverb

Legal Definition

onerous

adjective

oner·​ous ˈä-nə-rəs, ˈō- 

1

: excessively burdensome or costly

2

: involving a return benefit, compensation, or consideration

an onerous donation

—used chiefly in the civil law of Louisiana see also onerous contract at contract compare gratuitous