ad·​verse | \ ad-ˈvərs How to pronounce adverse (audio) , ˈad-ˌvərs \

Definition of adverse

1 : acting against or in a contrary direction : hostile hindered by adverse winds
2a : opposed to one's interests an adverse verdict heard testimony adverse to their position especially : unfavorable adverse criticism
b : causing harm : harmful adverse drug effects
3 archaic : opposite in position

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Other Words from adverse

adverseness noun

Adverse vs. Averse

Many people find themselves confused when faced with the choice between adverse and averse. While these two adjectives have many similarities, they are not used interchangeably.

If you want to describe a negative reaction to something (such as a harmful side effect from medication) or dangerous meteorological conditions (such as a snowstorm), adverse is the correct choice; you would not say that you had an averse reaction to medication or that there was averse weather.

Averse is most commonly followed by the preposition to (as in "she is averse to shellfish"), but not in every case; you can, for example, describe someone as “risk averse." Normally, averse to signifies a degree of dislike and avoidance, but when preceded by the word not (as in “he was not averse to having another drink”), it may be used as a pointedly understated way to express an interest in something.

In short, adverse tends to be used to describe effects, conditions, and results; while averse refers to feelings and inclinations.

Examples of adverse in a Sentence

The Bankruptcy Code requires that debtor's counsel be disinterested and not have an interest adverse to the estate. Lawyers Weekly USA, 4 Oct. 1999 On more than one occasion his decrees provoked riots, and there were those who voiced adverse opinions on the Duke in public. — Alison Weir, The Princes in the Tower, 1992 The plant tolerates adverse conditions … — Dave Dunn, Fine Gardening, January/February 1991 all the adverse publicity really caused the movie star's popularity to suffer the adverse effects of the drug are too severe to allow it to be marketed
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Recent Examples on the Web That’s because anyone can submit an adverse event without medical record verification and there is no guarantee that every event is reported. Paul Sisson, San Diego Union-Tribune, 31 May 2021 The adverse event of the day with the most obvious potential bite may well be the Dutch court’s decision ordering Shell to dramatically expand its plan to cut greenhouse gas emissions. David Blackmon, Forbes, 27 May 2021 But a recent Reuters fact check of a similar claim concluded that the system accepts reports of any adverse event regardless of whether there was proof it was caused by a vaccine. Stephen Montemayor, Star Tribune, 26 May 2021 Anyone who receives a vaccine authorized in the United States can report an adverse event to VAERS, as can doctors, family members, and others. Meredith Wadman, Science | AAAS, 26 May 2021 After reports are made to the Vaccine Adverse Event Reporting System, the CDC and FDA then look to see whether the rate of an adverse event -- in this case, myocarditis - is higher than expected. Elizabeth Cohen, CNN, 25 May 2021 The most common adverse event was pain at the site of the injection, according to the study. Elizabeth Weise, USA TODAY, 25 May 2021 These black box warnings are the highest level of safety alert that the FDA can employ, warning users that a very serious adverse event could occur. C. Michael White, The Conversation, 13 May 2021 Social-media monitoring platform Zignal Labs Inc. said mentions of the rare adverse event have dropped online. Julie Wernau, WSJ, 9 May 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'adverse.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of adverse

14th century, in the meaning defined at sense 1

History and Etymology for adverse

Middle English, borrowed from Anglo-French advers, borrowed from Latin adversus "turned toward, facing, opposed," from past participle of advertere "to turn toward, direct" — more at advert entry 1

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Time Traveler for adverse

Time Traveler

The first known use of adverse was in the 14th century

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Last Updated

13 Jun 2021

Cite this Entry

“Adverse.” Dictionary, Merriam-Webster, Accessed 18 Jun. 2021.

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More Definitions for adverse



English Language Learners Definition of adverse

: bad or unfavorable : not good


ad·​verse | \ ad-ˈvərs How to pronounce adverse (audio) \

Kids Definition of adverse

1 : acting against or in an opposite direction adverse winds
2 : not helping or favoring adverse circumstances

Other Words from adverse

adversely adverb Bad weather adversely affected attendance at the fair.


ad·​verse | \ ad-ˈvərs, ˈad-ˌvərs How to pronounce adverse (audio) \

Legal Definition of adverse

: opposed to one's interests : operating to one's detriment an adverse verdict


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