So, in real-like fe, magic is a label applied to certain beliefs and practices to mark them in contrast to more socially acceptable beliefs and practices. Originally, it was defined in contrast to Christianity, and nowadays it is generally defined in contrast to science. As someone said earlier, Magic is what the other tribe’s priests do. I think it would be really interesting to see a D&D setting where this is the case. Cultures view the spells their religious leaders cast as “divine” and the spells cast by other cultures’ religious leaders as “arcane.” Non-religious magic users view their own spells as natural phenomena that they can reliably reproduce with the appropriate formula, no more magical than a simple chemical reaction, while common folk see the miraculous things they can do and call it magic.