Sushi is a Japanese food consisting of cooked vinegared rice (shari) combined with other ingredients (neta), usually raw fish or other seafood. Neta and forms of sushi presentation vary, but the ingredient which all sushi have in common is vinegared rice called sushi-meshi. Raw meat sliced and served by itself is sashimi. The original type of sushi, known today as nare-zushi was first developed in Southeast Asia possibly along what is now known as the Mekong River and then spread to southern China before introduction to Japan. The term sushi comes from an archaic grammatical form no longer used in other contexts; literally, sushi means 'sour-tasting', a reflection of its historic fermented roots. The oldest form of sushi in Japan, narezushi, still very closely resembles this process, wherein fish is fermented via being wrapped in soured fermenting rice. The fish proteins break down via fermentation into its constituent amino acids.
Contributions by DanielVonEhren, Dforest, and Jon Backenstose.