The French expression en route (meaning “on your way to”) is so widely used in English that it’s acceptable to not place it in italics every time you use it. What isn’t acceptable is replacing the en with on.
There’s an animated GIF doing the rounds which sums up the plot of every episode of TV medical drama House. It’s pointed and cruel and funny — but the effect was ruined for me by a spelling mistake in one of the captions.
I thought put the brakes on was an obvious automotive idiom and that everyone would be able to spell it correctly. Then I opened my eyes and realised that some people are writing put the breaks on instead. Oh dear.
The distinction between stationery (pens, pencils, binder clips and other office gear) and stationary (not moving) is the first spelling mnemonic I can recall learning. However you remember it, it’s important to get it right.
Breeches is a somewhat old-fashioned word for trousers, and one you probably don’t need to deploy often unless you’re heavily into riding gear or have scored a job writing Asterix comics. One context where you definitely shouldn’t use it? When you actually mean breach.
Language changes over time, and current usage needs to reflect that to be accurate. There was a time when “gaol” was the accepted spelling in Australia. But that time was 1954, not 2014. Jail is the correct spelling these days.