One word that tends to cause a lot of difficulty for my Russian speaking students is the word 'efficient'. Part of the problem is that there is no direct translation of this word in Russian. The word 'effective', however, does exist in Russian as 'эфективный' (effektivny) which, as you can see, is practically the same. So, when my students see 'efficient' they often mistakenly think it means the same as 'effective'.
However, while many people are both efficient and effective, it is possible to be effective, yet not efficient. Confused? You shouldn't be, because the words stress two very different things.
'Effective' stresses the positive result of something. For example, an effective language course is one that brings the desired result -- an improved knowledge of the language.
'Efficient' on the other hand, stresses speed and a reduction or minimization of waste. An efficient worker is basically one that does the job quickly and doesn't fool around and waste time.
When I was a teenager, I worked at Waldenbooks -- a big bookstore chain in the United States. Working in a bookstore, you tend to spend most of your time shelving books. Generally, you load up the new books on a cart and leisurely walk about the store shelving the books in no particular order. This of course in not very efficient.
Then the company called in an efficiency expert who walked around with a stopwatch and clipboard watching our every move -- something that made us all a bit nervous. After that, we had to go to a special meeting where the efficiency expert explained in meticulous detail how we were to shelve the books in a particular way and order to improve our efficiency.
Needless to say, we all hated this and promptly ignored the advice, returning to our inefficient ways as long as we were out of site of the manager. I nevertheless considered myself an effective employee as I loved helping customers find the books they needed and helped sell a good number of books.
So to summarize:
efficient = fast + no waste
effective = positive results
