Qki and magic are the two primary types of energy in the Gurhai universe.
Qki (pronounced kee) is physical energy. It is what is generated by physical movement and activity, and it is what can be used to enhance physical movement and activity. Every living, moving body has dynamic qki, which fluctuates in intensity and quantity as the body moves and rests; every immobile physical object has static qki. (For the purposes of simplicity, I'm going to class plants as having static qki - I know they move, but it's not quite the dynamic movement of a fleshy body.) Qki is inherently neutral and inherently bound to physical objects, and usually never leaves the physical object that generates it. Excess qki provides a body with extra strength, speed, endurance, agility, fervor, or healing ability, increasing the body's performance in one or more ways until the excess qki has been used up and performance goes back to normal. A dearth of qki decreases the body's peak performance in one or more ways and also slows healing. A total lack of qki is fatal to a living body if sustained for more than a few moments.
Magic is non-physical energy. It is what exists outside of as well as within living bodies and inanimate objects. Like air, its density varies greatly from place to place, and in some places in the universe, it is so thin as to be nonexistent for all practical purposes. (Unlike air, it is not required to sustain life. Qki is.) Magic is not generated by physical movement or activity, nor does it require physical actions to be manipulated. Pure magic, the kind that exists throughout the universe as a natural element of life, is neutral and referred to as 'arcane' magic. Arcane magic is quite powerful but also often difficult to manipulate; it is not refined and does not work well for deft or subtle spells. There are several 'types' of refined (non-arcane) magic: elemental magic*, demonic/black magic, and the Light being the primary types. Magic can be used, manipulated, gathered, stored, etc. external to any physical object or within inanimate objects or even living bodies. Objects and bodies alike have a limit to how much magic they can hold, and some have inabilities to hold certain types of magic.
*Elemental magic includes water, air, fire, earth/soil, stone, crystal, metal/ore, all kinds of weather, shadow, and natural (sun/fire) light.
Qki can be converted into magic and vice versa, but these are considerably difficult processes. To convert qki into magic, one must generate enough excess qki to spare without dying or faltering, then bring the excess qki outside of the body; the process of separating qki from its physical counterpart converts it into concentrated, unrefined, and occasionally impure arcane magic, which is very powerful but hard to control. (That kind of qki-turned-raw-magic has a particular force and texture that makes it unaffected by more refined spells or shields. A body that is very magic-resistent will be vulnerable to it; a body that is very qki-resistent but magic-sensitive will be strongly resistent to it, but it will affect the body more than pure qki would. It is, in essence, an extremely condensed form of the unrefined arcane magic that exists throughout the universe.) To convert magic into qki, one must have sufficiently condensed magical energy or a sufficiently large quantity available; qki is a much thicker, more solid form of energy than magical energy of any type. Magic-to-qki conversion is a physical/involuntary action/skill that cannot be consciously taught or learned; it is something that, in theory, most species are capable of doing, but only a very few ever actually accomplish. When presented with a severe lack of qki, whether because qki level is dangerously low or because the body is about to attempt a feat that requires a lot of extra qki, the body absorbs and processes nearby available magical energy. (Shapeshifters - the tahori and their next-of-kin - are the ones who do this most regularly, since shapeshifting requires a lot of qki to change the physical body so quickly and painlessly.)
Qki and magic are not proportionate to each other. A body can have a very low max-qki limit and a very high max-magic limit or vice versa. Each living body has a starting set of limits for both qki and magic (and occasionally different limits for different types of magic, normally seen when a body cannot handle a certain kind of magic; see affinities below); this starting set is determined by species, environment, and less influentially by individual genetics. A resistance can be developed that locks down the current limits and refuses extraneous magic/qki entrance into the body, thus reducing magical/qki effects on that body but disabling that body's ability to improve its qki and magic capacities. However, qki and magic limits can be changed over time; for the most part, the limits increase with age and ability naturally, or increase further with conscious training, but some lifestyles induce a reduction of qki/magic limits. (Limits are rarely consciously reduced.) Those who are extremely physical have higher qki limits naturally; their bodies engage in exercise, activity, and physical exertion frequently enough that their ability to generate qki and make efficient use of excess qki is honed. Those who are physically sedentary have lower qki limits that occasionally dwindle over time, but they also have a high change ability; if they were to switch to a physically demanding lifestyle, their bodies would adapt and raise the qki limits very quickly, compared to the gradual increase over time in an active body's qki limits. Similar principles apply to magical energy and limits; those who use magic regularly will increase their body's ability to both manipulate and to store magical energy. (Note: Limits on magical energy do not increase in leaps and bounds at any time, unlike the potential qki limit increase in a newly-active body. The change of a magical energy limit is always gradual, and even after being well-honed, in many cases the max limit will dwindle over time unless a body continues using a very large amount of magical energy regularly.)
In some (but not all) cases, a body will have a magical affinity. (Having a magical affinity is also called being attuned to a certain kind of magic.) Although a magical affinity is defined as having an innate talent for using/sensing/storing one particular kind of magic, it can also include bodies who have varying limits to certain magic types, as well as bodies who cannot use one magic type at all but can use others. In many cases, one who has an affinity for magic type X will be unable to use any other kinds of magic, rather than just being exceptionally skilled with X and average with the rest. Affinities are not consciously chosen; they are quite physical, based on species, environment, and individual genetics. Some entire species have a racial affinity, though its intensity can vary across individuals.