An Arcanum (plural. Arcana) is one of ten divisions of the Tapestry. Each Arcanum originates from one of five Supernal Realms; each Supernal Realm is the source of two Arcana and each Arcana can be represented by a color for its Supernal Realm. The Arcana are divided by what the mage seeks to change: Life, Death, Force, Fate, Matter, and so forth. Each “color” on the diagram below is a point in a 5-point star, and each line connecting the stars represents a different Arcanum. The Arcana act both in unity and in chaos, working against its opposite natures as much as it cooperates with its neighboring Arcana. Thus each Arcana are aligned closer to certain Supernal Realm than others and both function together better as spells and are easier to learn in addition. For instance, a mage of the Life Arcanum finds it easiest to work with its complimenting Arcana of Forces and Spirit. Using the color wheel as an example, the further from one Arcanum you go the more difficult it is to learn and master.
Very interesting explanation.