Efficient and effective. This is a typical example of the principle of knowing (at least) two translations for each Slovak word (a vice-versa), and in this case it applies whether you want to translate the 'proper Slovak' "účinné" or the 'Latin Slovak' "efektívne", because the latter doesn't always mean effective in English. The use of these words depends on the difference between the ideas of 'process' and 'product'. Activities are efficient if they work well, properly, economically (úsporne) and dynamically - the focus is on the process. Actions (some activities too) are effective if they produce an effect, an outcome or a result - the focus is on the product. Hybrid-powered cars are said to be more efficient (but not effective) than conventionally-driven ones. Laws and regulations can only be effective (but not efficient) if they are consistently enforced.