Donburi is a Japanese "rice-bowl dish" consisting of fish, meat, vegetables or other ingredients simmered together and served over rice. Donburi meals are usually served in oversized rice bowls which are also called donburi. If one needs to distinguish, the bowl is called donburi-bachi and the food is called donburi-mono.
The simmering sauce varies according to season, ingredients, region, and taste. A typical sauce might consist of dashi (stock broth) flavored with soy sauce and mirin (rice wine). Proportions vary, but there is normally three to four times as much dashi as soy sauce and mirin. For oyakodon, Tsuji (1980) recommends dashi flavored with light soy sauce, dark soy sauce, and sugar. For gyūdon, Tsuji recommends water flavored with dark soy sauce and mirin.
One can make donburi from almost any ingredients, including leftovers.