Meaning of FUNCTIONAL in English
[func.tion.al] adj (1631) 1 a: of, connected with, or being a function b: affecting physiological or psychological functions but not organic structure "~ heart disease"
2: used to contribute to the development or maintenance of a larger whole "~ and practical school courses"; also: designed or developed chiefly from the point of view of use "~ clothing"
3: performing or able to perform a regular function -- func.tion.al.ity n -- func.tion.al.ly adv
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012