Meaning of EFFECTIVE in English

[adjective]Something can be described as effective if it produces the results that it was intended to.It's a very effective cure for a headache.The lighting for the production made a very effective use of shadow.See also effective at effect (USE).A person can also be described as effective if they are skilled in a particular way.She's a very effective teacher.You can also use effective to mean in fact, although not officially.Although she's not officially our boss, she's in effective control of the office.

Cambridge English vocab.      Кембриджский английский словарь.