Language of Magic
Magic is written in a Runic language. This language was discovered in early history and is the core to using magic effectively. When mages want to use magic they envision the runic language in intricate patterns to determine the effects they wish to use and then invoke it's power (by imparting their energy into it). While technically possible to use magic innately without the runic language, doing so requires incredible amounts of power. So much power that entire disciplines were created to combine the power fo more than one mage to create effects early on to match the effects of creatures which were innately magical like the Fey.