D&D New Edition: Arcane Power Source

Simply enough, the Arcane power source is defined by its focus on spellcasting. Most other power sources include a spellcaster, who mixes their own source's talents with magic, but all Arcane users can snap off a few cantrips at least. In general, Arcane power source characters have more raw spell power available than anyone else. While a Mageblade might not measure up to a Cleric in terms of raw power, that same Cleric would fall short of a Wizard.

The other important differentiation from other magical classes comes in the form of talent. Arcane casters are best with spells and abilities that manipulate elemental energies, create energy or matter from nothing, and alter the fundamental workings of magic. They can in theory access any spell that a Cleric might, but they lack a Cleric's natural skill with affecting life energies, or a Psion's ability to manipulate the minds of others.

Arcane characters work magic into most things that they do. An Adept is not simply a Rogue who can cast spells - he works his magic into every action, from his cloaking invisibility to spell to the telekinetic theft of the keys to the spider climb spell which helped him scale the prison wall.