Good evening, dear friends. I sincerely hope that Admin of this forum will agree to give his generous permission to dedicate this page to particular detalis of English, that are important for those who already have a good command of this language, but sometimes encounter specific peculiarities that raise difficulties. Efficiency and effectiveness. Which of these words corresponds to the Russian "эффективность", and which - "действенность"? Explanations to both are given below. I won't object if you remove this topic; I acknowledge that it a bit dissonates. Excuse me for prolonged non-responding to the messages addressed to me in Bulgarian and Polish sections; but I'm currently infernally busy. Thanx.