Todd L Ross
Much like the question of whether or not a hot dog is a sandwich (it isn’t, really), the answer here depends on how you define the terms.
Here’s the Merriam-Webster definition of soup:
“A liquid food especially with a meat, fish, or vegetable stock as a base and often containing pieces of solid food.”
While you could make the case that a cereal qualifies as a “liquid food,” it’s not made with any sort of stock, so most people would say that it doesn’t qualify. We’d add that soups are generally cooked, or at least, subject to some sort of a process of preparation; cereal just consists of flavored grains tossed into a bowl and covered with milk.
Another point that gets brought up often in this debate: Most people think of soups as savory concoctions, but cereals are rarely spicy or salty. Store-bought cereals are often sweet, which, again, goes against the traditional idea of a soup.
Still, some people will argue—at length—that cereal qualifies as a soup. Writing for The Chimes, a Biola University publication, Christian Leonard noted that milk could qualify as a “stock or broth,” and that Sweden boasts many traditional sweet soups. “The taste of the ingredients, therefore, has no bearing on whether a dish is considered a soup.”
“Cereal is a liquid-based food which contains a solid component,” he wrote, and that’s good enough for him.
Leonard’s editorial is largely tongue-in-cheek (he later proclaimed that “every physical object is a soup, bread, salad or a combination of two or three”), but he makes a compelling case. Even so, words derive their meaning from common usage, and if you asked someone to “hand me my soup" after leaving a bowl of Trix sitting on your kitchen table, you’d likely be met with confused looks. To most people, a cereal is not a soup.
If we were trying to describe cereal in milk and we couldn’t use either of those terms, we might call it “pressed grains in a dairy sauce.” If you’re looking for a ridiculous way to describe your breakfast, we’d go with that.