- In probability, don't toss a coin and get a head. In a room full of teenagers, far better to flip a coin and get a tail.
- Avoid examples involving 'balls in a bag'. 'Discs in a bag' can be just as problematic if not said clearly. Try counters instead.
- Also in probability, be careful how you say 'the or rule'. Spare a thought for language teachers who have to administer oral exams.
- When writing on the board do not shorten the word cumulative. Cum freq is likely to cause a stir.
- Don't make c proportional to k (c∝k).
- Careful what you say (and how you gesture) when talking about enlargements, top heavy fractions and going down the number line.
- Be prepared for giggles if an answer is 69.
- Avoid having refer to 'the d' or saying 4q ('4q too!').
- We can't avoid f(x) but be prepared for 'f off' silliness. Avoid f(u).
- When writing page numbers on the board, beware of p155.
- If you're making nets in class, you'll need to include tabs (not flaps) for sticking them together.
- Don't say cos. Say cosine. Cos Omac is an insult and certainly not suitable for a maths lesson if any of your students speak Arabic!
Teenagers, eh? Bless 'em.
Incidentally, if you hear references to words you are unfamiliar with (belfie?!), this guide might help.