adverse vs. averse

As the public/pubic and Hadron/Hardon typos show, a single letter can make all the difference in a word. Luckily, changing one letter in a word doesn’t always lead to an embarrassing typo. But it can still change the meaning of a word. In this post, we’ll talk about the difference between two commonly misused words that differ by just one letter: adverse vs. averse.


Let’s start with adverse because it’s the more common word in the pair. (Our Google search produced 118 million hits for adverse but only 13.4 million for averse). Adverse is an adjective that means unfavourable, negative, or suboptimal. We use it in sentences like these:

  • “We were delayed because of adverse weather.”
  • “You must report all adverse events that occur during the study.”
  • “The medication had adverse effects.”


Okay, so we now know what adverse means. So what’s the difference between adverse vs. averse? Like adverse, averse is an adjective that refers to something negative, but is does mean something different. We use averse when we want to describe a negative feeling toward something. For example, we would use it sentences like this:

  • “He is averse to exercise.”
  • “Milos is averse to store-bought pet food but will eat it if he can’t tell what it is.”
  • “Senior leadership is averse to change.”

How Do I Remember Whether to Use Adverse vs. Averse?

Adverse vs. averse are both adjectives that mean something negative, so how are you supposed to know which one to use in a certain sentence? Take a look at the example sentences in each section above. Do you notice a difference between the two sets? (Hint: focus on the words that adverse vs. averse describe).

In the example sentences, averse describes only people or animals (i.e., he, Milos, and senior leadership). This makes sense because averse describes a negative feeling. And we know that it’s typically only people and animals that can feel things. Adverse, on the other hand, describes only inanimate objects (i.e., weather, study events, and effects of medication). So if you’re trying to keep adverse vs. averse straight, remember that averse is usually for describing people and animals whereas adverse is usually for describing things.


Adverse vs. averse may seem confusing because they look similar and mean similar things. But the good news is that you can keep them straight by remembering that they describe different types of words. Use adverse to describe a negative event or condition and use averse to describe a negative feeling someone has. If you can remember this, mixing up adverse vs. averse is a mistake you’ll never make again.

Want to read about other commonly confused words? Check out our post on the difference between peak, peek, and pique.
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Adverse vs. averse: What’s the difference?
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