What do we call a group of workers in the same trade in a medieval town?

The story behind the answer

In medieval towns, associations of people in the same craft or trade set rules for quality, prices, and training. They controlled entry into the profession through the apprentice–journeyman–master system, requiring a “masterpiece” to gain full status. They also provided mutual aid, funded chapels and charities, and held significant influence in city politics, often securing monopolies over their craft within the town.

To clarify the options: a brotherhood was primarily a religious or devotional fraternity; a guildhall was the building where members met; and while some bodies had corporate charters, “corporation” is a later legal term not specific to these trade associations. Merchant and craft associations shaped urban life, from London’s livery companies to the Hanseatic League’s network of trading cities.