This category is for magical systems, martial art schools (rather than the physical schools... the gather technique concepts of the art), combat systems, legal systems, systems of weights and measures, calendars, languages.

Agriculture/ Husbandry        
Pieces dealing with the growing, gathering, and herding of food and organic resources.
Pieces dealing with the appearance and creation of permanent and semi-permanent structures.
Pieces dealing with the production and performance of artistic endeavors, and artistic styles.
Combat/ Warfare        
Pieces dealing with fighting, sparring, war, and combative sports.
Pieces dealing with the second oldest profession and the organizations that practice them. This is the area of shadows - theft, murder, and crime for a variety of purposes.
Divine/ Spirit        
Pieces dealing with the Gods, Spirits, and Religions (organized and not). The thergical aspects of existence
Pieces dealing with lifeforms (critters and plants) and how they live together and in relation to their environment.
Geological/ Geographical        
Pieces dealing with the physical environment and the imposed boundaries of states and other bodies.
Pieces dealing with any area of knowledge not covered by another area AND the collecting, sorting, and storing of any knowledge and lore. This includes cryptography.
Pieces dealing the buying, selling, and trading of things and the economy in general.
Pieces dealing with thaumaturgical (wonder or miracle working) systems (magic, psionics, bardic, etc). Thergical elements associated with a specific thaumaturgical system are allowed.
Pieces dealing with the governance of people, their structures and processes. It also deals with how social groups interact.
Societal/ Cultural        
Pieces dealing with social structures and conventions, including laws, standards, and cultural codes.
Technical/ Mechanical        
Pieces dealing with any form of tangible technology - machines, tools, materials, and processes.
Pieces dealing with the moving of people and goods.
The system, if utilized, defines the game world. Mostly used for magic/ mystical systems or Divine/Spirit systems, but other areas can help to define their setting.
The system can be incorporated into any setting/ campaign with a minimum of effort.
The system is based on historical or settings in our world.
The system is based upon a specific setting.