Weary or wary seems to me to be an odd pair to mix up – sorry if you do this and don’t think it’s odd, but they just seem so different. Having said that, I do keep seeing them being mixed up, so this will probably be helpful!
I see weary being used where it should be wary more than the other way round; I have a feeling that perhaps a memory of leery is getting into it, and then the pronunciation means the writer goes for the word that sounds like leery. Who knows. Anyway, here we go:
Weary means tired. And to weary of something means to be reluctant to experience any more of it. “I’m weary, because I’ve worked 10 hours today” (this is not literally true, don’t worry!). “I’m weary of writing Troublesome Pairs posts and I don’t think I’ll do it any more” (this, also, is not true).
Wary means cautious about possible dangers or problems. It’s linked to beware, and maybe that will help people to remember it. “I’m wary of dogs after being bitten a few times”, “I’d be wary of going down that dark alleyway if I were you.”
Let’s see if we can use the two in the same sentence … “She was weary of being wary, jumped into the middle of the pack of dogs … and got bitten.”
Sorry, dog lovers – please feel free to substitute any other biting animal in these sentences!