My favorite similar mixup is ordinance vs ordnance. Though I suppose they're not mutually exclusive. I'm sure that printed copies of some bylaws are hefty enough to cause serious damage if you lob them at the enemy.

This was hilarious when I saw local businesses put up signs requiring masks due to local "ordnance". I had to wonder what kind of masks they expected us to have

insure vs ensure is another one I've commonly seen. As in "please insure that <some task> is complete".

Interestingly, I think this was correct or at least colloquially correct a few centuries ago. I've seen that spelling used in text from the 1700s and 1800s by educated people. Probably a holdover from before spelling got really standardized.

Glad there’s someone else pedantic here so I don’t have to do it…

One aspect of this mix-up that I enjoy is the fact that deprecating something causes its value to depreciate, by quite a lot!

not only can deprecate cause depreciation, it can be a synonym for depreciate (in the financial meaning). but depreciate can't be a synonym for deprecate (in the end-of-life meaning).

just one of those fun things that gets thrown in to make sure nobody ever fully understands the english language.

As a Swede reading OT comments on HN I can ensure you that deprecate and depreciate are not words I would mix up unless autocorrect gets me. They look similar after all.

Ordnance and ordinance I don't even know the difference between though.