I was learning some of the syntax of Arduino code using a sketch made by others and came across the #define. I looked it up in the reference where it explained what the command did.
It also said to use "const" instead of "#define" because of potential problems with the latter in code.
So I changed them, compiled and received errors on each one I changed. So I changed them back.
It's not a big deal, but there is some ambiguity with the reference in this regard.