I SHOULD know this...!

I dont know exactly why I was pondering this, but the other night I wondered to myself why the second 'A' in Canada changes sounds when the word is changed to Canadian. In 'Canada' it makes the 'ah' sound, while in 'Canadian' it makes the 'ay' sound.

Then I realized that, as an English major, I should be thinking in terms of 'long vowels' and 'short vowels'. But for the LIFE of me, I can NEVER remember which is which. I just had to look up which was which to find out that the Long Vowels are the vowels that sound like they are pronounced (the 'a' in Canadian), while the short vowels are softer (the 'a' in Canada). And even though I studied this all through grade school and am a current scholar of the English Language and Literature, I can almost guarantee that I will not remember which are which in the morning.

What are some of the simple facts or bits of knowledge that you can never remember, but you should, because its part of your major or you're constantly reminded of it, or it should just be something that everyone knows?

Jam it back in, in the dark.