A guild is an association of artisans who control the practice of their craft in a particular town. The earliest types of guild were formed as confraternities of workers. They were organized in a manner something between a trade union, a cartel, and a secret society. They often depended on grants of letters patent by a monarch or other authority to enforce the flow of trade to their self-employed members, and to retain ownership of tools and the supply of materials. A lasting legacy of traditional guilds are the guildhalls constructed and used as meeting places.
An important result of the guild framework was the emergence of universities at Bologna, Paris, and Oxford around the year 1200; they originated as guilds of students as at Bologna, or of masters as at Paris.