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.
Focus
Agriculture/ Husbandry
Pieces dealing with the growing, gathering, and herding of food and organic resources.
Architectural
Pieces dealing with the appearance and creation of permanent and semi-permanent structures.
Artistic/Performance
Pieces dealing with the production and performance of artistic endeavors, and artistic styles.
Combat/ Warfare
Pieces dealing with fighting, sparring, war, and combative sports.
Criminal/Espionage
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
Ecological
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.
Knowledge/Lore
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.
Mercantile
Pieces dealing the buying, selling, and trading of things and the economy in general.
Mystical
Pieces dealing with thaumaturgical (wonder or miracle working) systems (magic, psionics, bardic, etc). Thergical elements associated with a specific thaumaturgical system are allowed.
Political
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.
Transportation
Pieces dealing with the moving of people and goods.
Scope
Defining
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.
General
The system can be incorporated into any setting/ campaign with a minimum of effort.
Historical
The system is based on historical or settings in our world.