Its always been that dollar sign comes to my mind first. I do not know why but its the currency that I have known to have ever since. It will always be the fiat but I need more bitcoins and other coins now, I will just trade it to dollars for me to live my dreams and to survive for the future.
I always think that currency is about the exhange of money of two countries. It's the state of the value of their own money. When currency comes up to my mind I think that it is the value of money of my own country and it has a corresponding value to the money of other countries. Currency is just the basis of how strong the money is.