Math in America vs. Maths in Australia - new vocab for y'all

I spent a good chunk of my summer watching pre-recorded webinars by Texas Instruments to try to master how Australians use the TI-Nspire to meet Australian national learning objectives.  As a side benefit, I also picked up on some Australian maths vocabulary.  Here's what I learned from the webinars:

Math = Maths

Slope = Gradient

"Pi over 3" = "Pi on 3"

"Negative 9" = "Minus 9"

Trig functions = Circular functions

Zero product property = Null factor hypothesis

Today, my first day with my very bright year 10 students, I was schooled but good on other maths vocabulary I hadn't yet picked up.

variable = pronumeral

power = index

"three to the fourth power" = "three to the power of four"

"x to the fourth power" = "x-four"

 (yes, you can probably hear the howling in my head from wherever you are right now on that one)

Irrational number = Surds 

This last one really flummoxed me; the rest one could reasonably trace the origin from American to Australian, or vice versa.  Surds -  no idea.  I asked another maths teacher what surds were, and he said "irrational numbers," then asked what I would call them.  I replied, "Um . . . irrational numbers?"  I can find no decent etymological explanation for this one, and I feel ridiculous saying it, but it's in the textbook and everything.
  

Also symbols - I used a dot to indicate multiplication; my year 10 students said they had no idea what it was.  I used a script "x" for the variable, they said I needed to make it like this: 




This bothered me, too, because if I can't use a dot to indicate multiplication, only an x, I can see great opportunity for confusion in simplification problems.  The x and script x are too close, in my opinion.  Strange that no one in Australia has asked for my opinion yet, after my big one day teaching . . .

Joel thinks any of these terms are optional, that he learned "variable" not "pronumeral", and wonders if the boys were just messing with me.  But Australia has a  national curriculum that I'm pretty certain has come out since Joel has graduated high school, so required vocabulary could have changed.

Matrices are up next.  Vocabulary looks pretty familiar.  Thank goodness.