confluence
Meaning: a gathering together
Usage: A confluence of different factors made tonight the perfect night.
congregation
Meaning: a gathering of people, especially for religious services
Usage: The priest told the congregation that he would be retiring.
caucus
Meaning: a meeting usually held by people working toward the same goal
Usage: The ironworkers held a caucus to determine how much of a pay increase they would request.
aggregate
Meaning: a whole or total formed by combining many parts
Usage: The teacher calculated the aggregate score for the whole class.
convene
Meaning: to call together
Usage: Jason convened his entire extended family for a discussion.