Magic

Magic is, to put it simply, the science/art of causing change to occur in conformity with will. It is influencing the course of events by means of supernatural forces in order to make what you want to happen happen. Of course, like most things, this is easier said than done. While the exact nature of magic is still largely unknown, enough information has been gleaned over the years to know how it generally works.

Magic is defined by human thought. This allows for flexibility in everything from casting to enchanting to potion-making. It's also why wizards use a variety of non-native languages to cast spells. The words simply help the wizard shape exactly what they want the spell to do in their minds. Amateurs need rituals, lengthy chants, and meditation to do even simple spells while more experienced wizards can do the same with a single word. Using a non-native language allows the magic to become linked with the word in your mind. If you just use the word "fire" for fire spells, you'll be burning your house down within a week. Words become less necessary, however, as a witch increases their skill and knowledge. For this reason, magic words are often considered to be the magic equivalent of 'training wheels."

Magic is generated by a variety of sources, primarily living things and emotions. Magic can be affected and fueled by emotions. Powerful emotions like rage, fear, happiness, etc. can make spells more powerful than usual or even fuel spells by themselves, but any sort of delicate magic, such as complicated rituals, requires total calm lest they backfire and blow your head off. For this reason, magic can be targeted using connections between objects. A spell can be targeted against a person by using a sample of hair, skin, or blood, or an object can be tracked by using a small piece of it.

It should be noted, though, that using magic physically tires out the spellcaster. Throwing around magic wears one out like doing any other act of physical exertion, and expending lots of energy can make one black out if used too quickly or too hard. And just like doing a lot of physical activity builds up muscle, casting a lot of spells builds up your ability to cast them. In addition, magic is bound by the laws of physics. For example, wind spells still need air to move, fire spells suck the oxygen from an area (and the energy can be drawn from ambient heat), and force spells still operate based on Newtonian physics. Beings with super strength are helpless if airborne, for example, as they are at the mercy of physics without anything to push against.

All humans are capable of using magic, with enough study and practice. Like any learned skill, though, some tend to be better at it than others. Unfortunately, most humans aren't even aware that magic actually exists, usually chalking up such phenomena to people with superpowers or other similar reasons. This is largely due to a combination of magic users dying or being killed off (especially in witch hunts) without passing on their knowledge and those sufficiently skilled in magic keeping their knowledge hidden from the public. Despite this, magic use has become common enough in parts of the world that magic users have come together to form whole communities and pass on their knowledge through tutoring and even through certain educational institutions.