It's about density and available space. I don't think most people around here think of Cambridge as a suburb of Boston. I'd say Newton is a suburb of Boston. Le

It's about density and available space. I don't think most people around here think of Cambridge as a suburb of Boston. I'd say Newton is a suburb of Boston. Lexington too. But not Cambridge or Somerville. Suburb evokes lots of single family homes with yards, and a fairly car-centric environment. That doesn't fit Cambridge, which is much more urban. That said, there are ultra-wealthy pockets of Cambridge that look and feel a little more like a suburb, but they are small. Like SF, Boston is somewhat unusual in that the city itself is pretty small both in surface area (48 sq miles) and population (~685k). The Greater Boston area is a different story, of course (cf. https://en.wikipedia.org/wiki/Greater_Boston https://en.wikipedia.org/wiki/Greater_Boston). But that includes Cambridge, and Somerville, and all the neighboring cities to Boston. Someone else in this thread said that Cambridge is to Boston like Oakland is to SF. That sounds about right, though Oakland is much bigger (both in population and surface area) than Cambridge.