Magic refers to the knowledge and practices held by magus, which could be thought as priests or people with high knowledge in the subject.
So the word magic in its pure form refers to craft of the wise (wo)men.
You have two different approaches to that word, apart from the trickery meaning (illusionism, which anyway is quite related to one of the concepts):
* A sort of knowledge you don't understand. Then you say magic is a hidden knowledge totally beyond what you understand about the reality.
* A modern definition totally varies depending on the tradition:
+ Wiccans say it is the force of nature. Every soul can cooperate with nature spirit (in the form of a god and a goddess) to make them bend their laws for a while and produce an effect.
+ Christians would say like it is a Devil's craft (this definition is not new but it is still held today, in the world of science and information). Actually magic is (under the hoods) the Devil fullfilling favors to you if you vow to him, and has the limit of what the power of the Devil can provide you. This is true, at least, for catholicism.
+ Kaoists say magic is the ability to bend (or twist, even break) the rules of reality according to your will. A common phrase there is everything is true.
+ Andean people held no difference (and still hold no difference) between magic and what they understood as science.
They have in common that magic, as a craft, is mainly an act of will, instead of a life-agnostic matter of fact.
You can take these alternatives:
* Reality is quite predictable, and acts of will do not actually exist. You can invent the concept of magic in a despective way for pseudoscience pretty much our reality does. Here: magic is not an actually useful concept outside of epistemology.
* Reality is quite predictable, but (uncommonly effortful) acts of will performed by some species or every live specie can alter the laws to an extent we could understand at some degree. 227
You could use the concept of magic there as a physiological or spiritual known effect related to a singularity. Here: both magic and science are useful here, and magic could be studied inside science.
* Reality is quite predictable on isolated environment, but acts of will are quite frequent. You can ask yourself if there is need for a difference between science and magic: Would you actually hold the current (ours) concept of science when the reality is just... volatile? The initial reaction of the people will be trying to understand why the acts of will occur, and the only science that will exist is one involving what we call magic. The science concept will be entirely useless if the magic could not be studied (although commonly executed) at all. Here: Science and magic could make a hybrid knowledge, perhaps only either of the words would be used and not both.
* Reality is not predictable since the minimal act of will can alter it. Then you don't have, perhaps, even a surviving society under those rules. Not only magic or science will be useless under that reality: the very concept of knowledge will be meaningless there. Here: Using a word for something not useful (because there would be no concept of reality) at all in an unpredictable reality is totally meaningless, so there would be none, if either life was possible there. 283