noun
menu (at a Chinese restaurant)
Specifically refers to a menu in a Chinese restaurant setting; not a general menu term.
中華料理店で菜単を見て注文した。
I looked at the menu at the Chinese restaurant and ordered.
General term for menu in any type of restaurant; 菜単 is limited to Chinese cuisine contexts.
Compound of 菜 (sai, 'dish, cuisine') and 単 (tan, 'list, bill'). The exact historical derivation is uncertain, but the word is conventionally associated with Chinese restaurant menus.