I am fairly confident that I have a decent understanding of the differences between 'extra' and 'excess', but there's been one specific context that had me scratching my head as of late. Say I want to express that I brought an ample amount of money (way more that I'd likely need) to spend at a cash-only store, which of the two words would be more appropriate? For example:
I was just short at the checkout last time, so I brought EXTRA // EXCESS money with me today.
To share my own thoughts, I feel that 'excess' has a retrospective vibe to it, as in you'd only know you have more than you need after the event. But 'extra' doesn't seem to be the perfect fit either, as it conveys that you already know exactly how much you will spent/need and just add an additional amount to that. (e.g. I know the stuff I am going to buy cost $200, but I brought an extra $50 just in case I might want to pick up some other stuff along the way.)
Note that the paragraph above is just my personal view. I would like hear a comprehensive answer that would confirm my understanding as well as correct it. Many thanks in advance.