A monadic operation is a type of function or operation in which a single argument is passed to a function, and the result of this function is also a single value. Therefore, some synonyms for monadic operation could include monadic function, unary operation, unary function, single argument operation, or single argument function. These terms all refer to a similar concept in which a function or operation takes only one input and returns only one output. It is important to understand these synonyms in order to be able to effectively communicate with others who may use different terminology or to better understand different programming languages.