Traditionally, Canada has a Big Five in its financial system: Bank of Montreal, Scotiabank, CIBC, Royal Bank of Canada, and Toronto-Dominion Bank. These five institutions dominate the nation's banking sector (See: Big Five Banks).
However, in recent years, Number Six has been elbowing into the action. The National Bank of Canada has gotten big enough that some observers have included it among the big boys and expanded the group to become the Big Six.
It's like how some people think Lake Champlain should be considered a Great Lake (and was briefly designated as such by federal legislation in 1998). In either case, it all depends on your definition of "Great." Or "Big."
