(countable) A convention is a large meeting of a specific group or for a specific purpose.
There's a doctor's convention in town this week and all the hotels are full.

The garden show will be at the convention centre.
(countable) A convention is an international agreement the controls how countries behave.
This action goes against the European Convention on Human Rights.

In my culture, a convention is to eat raw fish.
(countable & uncountable) A convention is a particular way of acting or a particular belief of a group of people.
By convention, people in North America drive on the right hand side of the road.

There are a set of conventions that every member must observe.

Noun