A list (for instance) is not a monad. A list plus appropriately defined unit_list and bind_list together form a tuple which is a monad. That's the 'is a' sense

A list (for instance) is not a monad. A list plus appropriately defined unit_list and bind_list together form a tuple which is a monad. That's the 'is a' sense of monads. When you refer to a list itself, it's easier to think of it as having the adjective "monaded" since unit and bind are defined even if you don't usually carry them around with you. A list is a monad/has the properties of a monad because the appropriate definitions of unit and bind both can exist and are written.