I will try to refine and add to these definitions over time. For now, I hope they suffice.
Essence: This is the constantly flowing fabric of the universe. It has no source, or destination. It can be thought of as similar to space-time. In this world it’s like essence-space-time.
Ki and Qi: These are the two energies within every cultivator. Qi is the body’s latent energy and, in other stories, might be referred to as life force, or something similar. Ki is the attuned essence that a cultivator keeps within their body. There are nine ki attunements that form a ring: -Fire-Lightning-Wind-Water-Wood-Earth-Metal-Shadow-Light-. Attunements are set in stone by the time a cultivator awakens. Most will have one major attunement, though many will also have a minor attunement, adjacent in the ring to their major attunement. In Immortal Anarchy, qi and ki are separate energies, but they can be cultivated in tandem, such as how Boneroot does it. This is not always the case. Increasing one’s qi will improve a cultivator’s stamina, strength, and other physical attributes. Furthermore, breakthroughs in qi cultivation will result in significant changes to a cultivator’s body, taking a step closer to their ideal form. Increasing one’s ki allows for the cultivator to store more of it within their body, improve their control over it, and increase the effectiveness of their ki techniques.
Cultivation and Meditation: Cultivation is achieved through meditation. Whenever someone is ‘cultivating’ that means they are meditating for the purpose of capturing more essence within their body, thereby improving their ki, qi, or both.
Cultivation Art: This is the collection of ki and qi techniques, cycling exercises, and meditation methods that form the foundation of a cultivator’s power. These are most commonly used by clans to train their youth, but there are also imperial cultivation arts used by members of the military, as well as sect arts, which are used by members of a sect who have no clan art, or wish to supplement their clan art.
Enchantment: An enchantment is a set of inscriptions, runes, or engravings used to give an item special properties. These are often done by two cultivators, one with the attunement matching the item and another with the attunement matching the desired enchantment. The most common targets of enchantment are weapons, robes, and armor, but it is also common to see enchantments for important buildings and other items.