Weary means tired or worn out. Wary means cautious, on guard. "Be wary of scams" warns you to watch out; "be weary of scams" says you should find them tiring. One letter, opposite advice.
The core difference
Two ordinary words separated by one letter and no shared meaning.
- weary — tired: weary travellers.
- wary — cautious: wary of strangers.
The construction that gives it away
Both take of, which is why the error survives: weary of means tired of, and wary of means cautious about. Both are grammatical, so the sentence reads fine and means the wrong thing. If you are warning someone, you want wary.
The related words
Beware and aware share a root with wary — all about watching. Weary is unrelated, from Old English.
Frequently asked questions
Is it "be wary" or "be weary" of something?
Be wary, if you mean be cautious. Be weary means be tired of it.
Why is the mistake so easy?
Because both words take "of", so either version is grammatical and reads naturally.
Is wary related to beware?
Yes — both come from a root meaning to watch, along with aware.