It’s not a shocker that these two adjectives are frequently confused. They differ in spelling only by a letter, and they both mean, broadly speaking, “opposed to.” Digging deeper into their etymology only reveals more similarity: the same Latin verb, versare, meaning “to turn,” is at the root of both.
To keep the memorizing simple, here’s a tip:
The word “averse” always applies to a person. It describes a person’s feeling or attitude of being against or opposed to something. Examples: She was averse to violent movies. Are you averse to attending this costume party?
The word “adverse” applies to outside forces and conditions that affect people, usually in a way opposed to or harmful to people’s needs or interests. Examples: A blizzard creates adverse driving conditions. This study concludes that violent movies have an adverse effect on children.
You’ll notice, too, that “averse” is almost always used with the preposition “to.” Examples: I am not averse to change; it just takes me a while to adjust to new things.
By contrast, “adverse” usually precedes a noun that it modifies: adverse side-effects, adverse winds
Get this distinction down, and then learn the more precise meanings of these two words by looking up the dictionary entries. And, finally, if you are familiar with “aversion” and “adversity,” which are the nouns formed from “averse” and “adverse,” knowing this quartet of words will strengthen your command of all of them.
P.S. If you come up with a mnemonic device based on the extra “d” in “adverse,” let us know.