탕 is Chinese, 국 is Korean, and 수프 is Konglish.
Is there a word for soup that isn't a loan word?
국수 or 국 or 탕, depending on the soups I've eaten, could all be translated to soup. 번대기탕, 쌀국수, 쑥국 (silkworm soup, rice noodle soup, mudwort soup).
I think 찌개 (jjigae) is a type of soup, too. Like 김치 찌개 (kimchi jjigae) or 된장 찌개 (doenjang jjigae).
I think 찌개 tends to be translated as 'stew', but then 찌개s also do tend to be a little soupier than the stews I've eaten back home.
찌개, 탕, 국 and 국수 all tread thin lines that I'm sure only a real connoisseur would be able to explain!
I would say 찌개 is a type of casserole
There isn't. We have love, eyes, the sky, trees, etc. all over the world, but everyone eats different foods in different places, so it's very unlikely that an English word for some food has a Korean equivalent.