Formal:
* Assembly: This implies a formal gathering of people for a specific purpose, such as a trade fair or market day.
* Congregation: Similar to assembly, this implies a gathering of people for a shared purpose.
Informal:
* Crowd: A general term for a large group of people gathered together.
* Gathering: A more general term for a group of people coming together.
* Throng: This suggests a large, densely packed crowd.
* Swarm: This implies a busy, moving crowd, often associated with a market's bustling atmosphere.
Specific to the type of market:
* Shoppers: If the marketplace is primarily focused on retail.
* Vendors: If the marketplace is focused on selling goods and services.
* Bargain hunters: If the marketplace is known for its deals and discounts.
Ultimately, the best collective noun to use will depend on the specific context and the overall tone you want to convey.