Tree-cat: a medium-sized feral feline found in the Central and North Canopies.
Tree-ether: a gas naturally occurring in pockets in the World Tree, tapped and harvested for use in dirigibles. May be distilled into a liquid.
Tree-gall: dregs left behind when Treesap is distilled and purified. Very flammable.
Tree-mines: man-made shafts sunk into the World Tree in order to extract certain products such as hardwood. Work in the Tree-mines is notoriously difficult and dangerous, and often accomplished by slave labour.
Treeology: a study of the layout, composition and characteristics of the World Tree, including climate, flora and fauna. Treeology courses for students at the seminary also include rudimentary navigation skills. Professors in Applied Treeology focus on plotting the movement of celestial spheres, alchemy and climatology.
Treesap: life-giving sap running through the branches of the Central, North and South Canopies, tapped and used by humans for a multitude of purposes. It is treated and hardened to make panes for windows, used for cooking, in preparations like glue and fermented to make alcoholic beverages. In the Eastern Canopy the Treesap has largely dried up, leaving behind a powdery residue called Tree-spice which is used in medicines and drugs.
Tree-water: naturally occurring reservoirs of rainwater caught in the World Tree. Some originate in the ice and snow of the Upper Fringes, creating quasi-permanent torrents through hollow channels in the Tree.
Tree-worship: Nurian term for Argosian religious doctrine. Nurians practicing the Eastern Doctrine maintain that Argosian priests have forgotten or twisted the original teachings of Saint Loa, substituting the ordinary World Tree for the divine Tree of Being.