IS world a proper noun or common noun or collective noun?

The noun world is a common noun, a word for any world of any kind. The noun world can also be a collective noun; for example:
  • a world of fun
  • a world of dolls
  • a world of shopping
  • a world of glamour.

A proper noun is the name of a person, place, thing, or a title; for example:
  • Disney World, Orlando, FL
  • The World Bank, (headquarters) Washington, DC
  • World Parkway Circle, St. Louis, MO
  • 'Guinness World Records' formerly known as 'Guinness Book of World Records'