It's a tricky instrument, the English language. Why, for instance, is cough not cow, when that well-known town in Berkshire is not Sloff, but Slough?
"Affect", you might reasonably explain, is a verb while "effect" is a noun. And then someone comes up with the phrase "to effect a transaction" and you're right back to square one.
But spelling is the real minefield. If your professional accommodation means that you definitely sit on a separate committee, you've probably made five errors before you've started.
And even those in the trade can't seem to sort out the two versions of statione(a)ry. I spotted a heroic, but wrong, attempt just the other day. "Buy your stationary here," the message in the newsagent's window proudly proclaimed. Presumably his envelope business was slow almost to the point of stopping. (In case you too are uncertain, that's the clue: "e" for envelopes.)
If you teach other people how to use this slippery language of ours, you can't help but notice the simple pleasure that some of them get when you slip up yourself. I once made the day of a student by telling him I needed to consult a dictionary for a word he was trying to spell.
We can get our own back, though, when we discover the errors of others. Examining bodies are particular targets. Aren't they supposed to be setting standards?
So what a joy it was to come across the following in a level 2 (GCSE equivalent) unit specification put out by the National Open College Network. The bugbear here was one of the other old language chestnuts: practice and practise. It is basically a question of whether you mean the noun or the verb. Thus "a doctor's practice" is spelt with a "c", whereas "to practise as a doctor" requires an "s".
In the unit in question, assessment criterion 3.2 says that students should be able "to practice in private study time". This is clearly a verb, not a noun, requiring an "s".
All right, you're no doubt thinking, but it's an error that anyone could make. Well, yes. But then the full wording of the assessment criterion is: "Practice spellings in private study time" and the unit title is improving spelling skills.