Sunomono is a term that refers to a range of vinegar-based Japanese foods and Japanese dishes. In Japanese, “su” means vinegar. Many Japanese foods, especially seafood or vegetable dishes, can be dressed in a vinegar dressing. Often times, sunomono refers to Japanese foods that are side dishes to a meal and accompany other Japanese dishes.
Generally speaking there are two types of vinegar dressing that are used on Japanese foods: Nibai-zu, which is a dressing that is made with equal amounts of vinegar and soy sauce, and sanbai-zu, which is a dressing that is made with equal amounts of vinegar, soy sauce, and mirin.
Sunomono dishes are closely related to namasu, which is a Japanese dish comprised of uncooked vegetables or seafood that has been thinly sliced and marinated in su, or vinegar. Marinating the foods in vinegar often leaves them with an acidic, pickled taste.