Does anyone have a mnemonic for x and y and which is which, on a graph? I feel like I have to look it up or guess every time. Some day a building is going to collapse because of one of my guesses.

Y has a vertical line in the character symbol, so it's the vertical axis on a graph.

@duckWit

Boom. Thank you.

@bahua let's keep those buildings strong and true 👍

Dead people in cartoons have X eyes so, X is for horizontal flat line :)
✖_✖

Things start at the bottom then raise, like your building.
Bottom before raising !
X before Y

X is a cross. Literally.

Umm, actually I just remember it. Also in 3d it totally depends. Sometimes you have xyz coordinates systems, sometimes xzy. Also in 3d you often have different references, in UE4 we have global (world), local and bone coordinates, just to mention a few.

No dude, what's difficult to remember is which one was the abscissa and which one the ordinate.
My mnemonic is a drawing I made of Visser 3 evening out a pile of papers.
I wrote "An Ordered Yeerk" beneath it. Now I'm always sure the Y is the Ordinate.

Y is up in the sky

I think the traditional system comes from the default line. When writing down numbers you write them from left to right. Voila, that's your x. Later it's like: oh, we also need another direction. So lets go... Umm ... Upwards, so it's called y. Later it's like: oh, where's the third thing? Oh shit, we need depth, that's complicated. Z.

@Jilano ah, a man of culture.