Magic, or Magik (plural magics or magiks) is a force in World of Warcraft that can bend the laws of physics and alter reality, from the simple to the extreme. Generally describes all non-natural effects (like most spells and powers on enchanted items) as opposed to natural effects (curses, diseases, and poisons). The distinction can get hazy at times.
It is also a Dispel Type.
In lore terms, the textbook definition of magic in Warcraft is an ever-present field of energy — the result of the Well of Eternity's waters being spread to the entirety of the world. While this is common knowledge, there was a great debate within the magical community regarding exactly how magic allows a user to manipulate elements of a plane of existence. The Kirin Tor were arguing if, say, fire was created because of physical forces dictated and powered with the help of magic or whether the fire was summoned from another parallel existence. Medivh believed magical fire comes into existence because the caster concentrates the inherent nature of fire in a certain area to summon it into being. Medivh also maintained that the practice of magic is "the art of circumventing the normal."
Forms of Magic
Two categories of magic exist, arcane and divine. Divine magic contains druidism, shamanism, voodoo, and holy light, as well as other religions. Nature is a subcategory within the divine, but a form of it can also be found in arcane as well. Runes are mystically ancient, it is a type of arcane magic, but accessed by more natural means (see Runemasters and Inscribers).
- Main article: Arcane
Arcane is the most common form of magic. Used by mages, wizards, and other sorcerers, such as those of the Kirin Tor, arcane magic is ever present in the atmosphere and accessible to any who are capable of drawing upon its energies. Arcane magics were discovered by the Kaldorei and later refined by the high elves of Quel'thalas and the human nations, and are most commonly practiced by mages. 
Arcane magic comes from the Well of Eternity, which itself draws from the Twisting Nether. Arcane magic is very powerful, but if not used carefully can cause corruption and great destruction. 
Another nature-reliant class, druids derive their power from the earth itself, although they do not require totems to channel energy like shamans. They become agents of nature itself, forming a bond with all beings of nature and pulling their strength directly from that bond. Night elves were taught druidism by Cenarius. Only beings who are directly attuned with nature are capable of adopting the power of a druid.
- Main article: Fel
The term Fel refers to the magics used by demons, more specifically, the Burning Legion. Fel energy is arcane magic at its most corrupt. If arcane magic is an addiction, fel magic is the embodiment of the drug at its purest form.
- Main article: Geomancy
Geomancy is a practice of divination and elemental combat native to several humanoid races of Azeroth. It is similar to shamanism in that disciples of geomancy wield the powers of the earth and encourage respect of earth’s spirits. The main difference between a geomancer and a shaman is the method through which the trust of the elements is gained. A shaman speaks directly with the elemental spirits, whereas a geomancer uses rituals, songs, and sacrifices to appease and propitiate the spirits.
- Main article: Holy Light
This magic was originally practiced by the Clerics of Northshire, a priesthood in the earlier days of Stormwind. The clerics and priests who practiced it believed their magic came from belief in the Holy Light, a set of ideals the church dedicated itself to.  This form of divine magic is used to protect and heal, and comes from the naaru. Divine magic was later practiced by The Silver Hand, the group of Paladins who developed a melee-based hybrid form of the magic.
- Main article: Necromancy
Necromancy is similar to the magics used by warlocks, however, instead focuses on the study of death rather than demonology. They are capable of reviving living creatures from death to do their bidding as undead servants.
- Main article: Rune magic
Runic magic was created by the titans. Their creation, the dwarves, quickly mastered the mysteries of the runes taught to them. However, as generations passed, the dwarves forgot their heritage and lost all knowledge of runes and their hereditary powers.
Tauren in Kalimdor rediscovered the power of runes. An ancient race as well, the tauren remembered the myths of runecasting and revived interest in this nearly lost art. The dwarves that came to Kalimdor with Jaina Proudmoore's Alliance Expedition learned tauren runecasting techniques. Tauren and dwarves do not share good relations, but they were eager to share knowledge of runes and titan myths.
The Vrykul practice a runic magic that even the most experienced wizards find unfamiliar.
- Main article: Shamanism and Nature Worship
The shaman's power is drawn from spirits, both of ancestors and of spirits found in natural surroundings. Shamanism is also practiced by some of the draenei who learnt shamanism on Draenor. In modern history, shamanism is common among orcs, tauren, trolls and draenei.
- Main article: Voodoo
Voodoo is a strange tribal mix between the power of arcane and divine magic, practiced by witch doctors and shadow hunters. They often combine reagents in a cauldron to create strange brews that most often result in bizarre transformations when consumed. They are widely known for placing hexes to morph victims into various creatures or placing curses.  The majority of voodoo users are trolls, although other races of the Horde have taken up the craft. 
Table of magic-using races
|Form of magic||Races|
|Arcane||Humans, Gnomes, Draenei, Forsaken, Trolls, High Elves, Blood Elves, Ogre mages, Night Elves (After Cataclysm), Ironforge Dwarves, Goblins, Worgen, Orcs|
|Druidism||Night Elves, Tauren, High Elves, Wildhammer dwarves, Trolls, Worgen, Furbolg|
|Fel||Demons, Orc, Forsaken, Blood Elves, Humans, Gnomes, Highborne, Ironforge Dwarves, Worgen, Goblins, Trolls|
|Geomancy||Pandaren, Quilboar, Troggs, Kobolds|
|Holy Light||Humans, Ironforge Dwarves, Draenei, Blood Elves, High Elves, Gnomes, Worgen, Goblin, Tauren|
|Necromancy||Nathrezim, Undead, Orc, Human, Forsaken|
|Shamanism||Orc, Tauren, Troll, Draenei, Furbolg, Tuskarr, Quilboar, Ogre, Dark Iron dwarves, Wildhammer dwarves, Ironforge Dwarves, Murlocs, Goblins|