Anko is the Japanese term for adzuki red bean paste, which is usually sweetened and used in wagashi desserts. It is sometimes also called an, which can refer to any sweet paste, or ogura, which specifically refers to a sweetened red-bean product. To refer specifically to a paste made with red beans, the word azukian should be used. It is called koshian when smooth and tsubuan when chunky.
Numerous red bean paste traditions exist in Asia. Anko, the Japanese style, typically does not have any added fats, unlike Chinese hong dou sha.
Note possible confusion with ankō, the Japanese term for angler fish.