All 3 Uses

convention
in
Up From Slavery: An Autobiography
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These were the ambitious youths of the race, at work with an earnestness that put to shame the conventional student life of most educational institutions.
Chpt Intr. *

conventional = normal or typical
When the Louisiana State Constitutional Convention was in session, I wrote an open letter to that body pleading for justice for the race.
Chpt 17 *

convention = large conference or meeting
Ignorant and inexperienced, it is not strange that in the first years of our new life we began at the top instead of at the bottom; that a seat in Congress or the state legislature was more sought than real estate or industrial skill; that the political convention or stump speaking had more attractions than starting a dairy farm or truck garden.†
Chpt 14

Definitions:

(1) (convention as in: teacher's convention)
a large conference or meeting
(2) (convention as in: conventional behavior)
something regarded as normal or typical
(3) (convention as in: The Geneva Convention)
a written international agreement
(4) (meaning too rare to warrant focus)