Why "Greater Toronto" rather than "Great Toronto"

Many big cities have their names preceded by Greater. Why not just Great? Does Greater indicate that the city is ambitious to expand itself?

Why is Greater not used for country names such as Great Britain? Is it just due to historical reasons?

In this context (greater Toronto) greater means “an area greater than the city itself” and “greater Toronto” is a shortened version of “the greater Toronto area”. Greater describes/modifies area rather than Toronto, giving a size contrast (greater) rather than describing the goodness of the city (great).

Great means big, greater means bigger.

So Greater Manchester is the larger metropolitan area around the city of Manchester in the middle.

However, Great Britain is the larger of the two separate and distinct Britains, the other being Brittany in north-west France. In French, Great Britain is Grande Bretagne and Brittany is just Bretagne. Brittany has also been referred to as Less, Lesser or Little Britain.

The answer is that the expression is based on how we, as humans, interpret geography. We refer to smaller, relatively unknown areas by the name of a larger, more well-known, area the smaller area is near.

By saying "Greater Toronto", we identify the city of Toronto and the smaller areas close by, at the same time acknowledging that these smaller areas are not, in reality, part of the city of Toronto. It is the same as saying "Toronto and its surrounding suburbs."

This nature can be observed when meeting someone unfamiliar to the area in question. If Sally lived in the suburbs of Washington DC, and met somebody from California at a conference, Sally would say "I'm from Washington DC", even though she lives in Falls Church, VA, and does not live within the boundaries of the city.

When someone asks me where I live, I would respond with "Charleston, WV" even though I don't live within the city limits, and the city is a 20 minute drive from my home.