Theoretically, a soup can be any combination of vegetables, meat or fish cooked in a liquid. It may be thick (like gumbo), thin (such as a consommé), smooth (like a bisque) or chunky (chowder or bouillabaisse). Though most soups are hot, some like vichyssoise and many fruit soups are served cold. Soups are often garnished with flavor enhancers such as croutons, grated or cubed cheese or sour cream. They can be served as a first course or as a meal, in which case they're often accompanied by a sandwich or salad.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.