I'm teaching the new organic chemistry student about functional groups. We reach aldehydes, and consider the formula of formaldehyde. I ask him what the next aldehyde would be called.
The student looks up, and with the innocent expression of the true imp, says: "Informaldehyde?"
If there is an angle between lines TR and RM, angle TRM (pronounced 'trum'), and you divide the sine of this angle by the cosine of this angle, what do you get?
...
OK, OK, I just asked you to name it, not to throw one.
Hee hee hee. I love this one. Hint: try looking up the trigonometric ratios and say it out loud.