noun
convention
kuhn-VEN-shuhn/kənˈvenʃn/
A formal gathering of people with shared interests or purposes.
Attendees at the convention listen as a speaker addresses the hall.

Etymology
A convention is literally a coming together. The assembly sense developed into a formal gathering of people for a common objective, matching today's meetings organized around shared interests.
In context
a meeting for 400 people tomorrow or even next week or next month although there is some short-term business that's usually smaller the larger groups and convention business has a much longer booking window
More examples
- The medical association holds its annual convention in Denver.
- Delegates at the party convention choose their presidential candidate.
- Comic book conventions bring fans and artists together.
Forms
convention · conventions
delegate noun — a person chosen to represent others
Similar words
- conference
- Often emphasizes presentations and discussion of a specific subject.
- congress
- Usually a formal gathering of representatives or specialists.
- assembly
- Emphasizes people gathered together, often for a single session.