Avgolemono is a family of sauces and soups made with egg yolk and lemon juice mixed with broth, heated until they thicken.
Avgolemono
Soup is a primarily liquid food, generally served warm or hot, that is made by combining ingredients of meat or vegetables with stock, milk, or water. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth. Soups are similar to stews, and in some cases there may not be a clear distinction between the two; however, soups generally have more liquid (broth) than stews.
Asparagus soup
Soup (William-Adolphe Bouguereau, 1865)
An advertisement for Campbell's canned soup, c. 1913
Instant soup in a powder form