1of or having a special activity, purpose, or task:a functional role relating to the way in which something works or operates:there are important functional differences between left and right brain (of a disease) affecting the operation, rather than the structure, of an organ: functional diarrhoea (of a mental illness) having no discernible organic cause:functional psychosis
2designed to be practical and useful, rather than attractive:a small, functional bathroom
3in operation; working:the museum will be fully functional from the opening of the festival
4 Mathematics relating to a variable quantity whose value depends upon one or more other variables: using functional notation, we can write—where L is the transactions demand for money
