In Polish "soup" (a general term) is "zupa" (loaned from French) and "stew" is "gulasz" (loaned from Hungarian), but can also be "duszone mięso", "mięso w sosie", "boef strogonow", and more - depending on specific way of preparation, size of meet chunks, way of serving etc.
In general, "zupa" is typically served before the main dish, as a starter, so it's more watery. Typically (not always) is served with pasta, potatoes, rice, chunks of vegetables, etc. inside. In fact, some soups do not even contain any meat, at all, like fruit soups, which resemble thin fruit compote. On the other hand, some other are really thick and calorick - especially those for winter season. For example "żurek" is really thick from flour, with meat and sausage chunks.
On the other hand, "gulasz" is a main dish, and is much more "thick". It's still served in bowls though, often with some bread on a separate plate. However some dishes ("duszone mięso w sosie") are served on top of pasta, potatoes, groats - and they are thick enough to be served on a regular, flat plate. Or contain only small amount of water to avoid spilling. So it really depends.
I'm not good at cooking, so I cannot create such a nice "scale", but on the "thinest" side I would place "smak na zupę" (water in which meat has been cooked) from which you can make variety of soups, depending on additional ingredients. Also "rosół" (a chicken soup) is quite thin. "Bulion" - very much depends on what you're going to do with it. Somewhere between "soup" and "gulasz" or "sos" ("sauce") there is "zupa-krem" or simply "krem" - quite thick, uniform, and typically do not contain solid particles - and typically made of