It has been scientifically proven that we forget about 80% of what we learn, on the average. Taking that into account, it´s quite normal that we get frustrated for forgetting something that we have been touch several times. This is even more common when you are at an intermediate level of communication in another language. You feel you understand what is said but you can´t produce orally with the quality you wished or needed.
Sometimes you are not even able to engage in more complex conversations because you lack appropriate vocabulary as you have a perfect command of your native language but not of the second language you are speaking. Perhaps you admire how people use idioms, phrasal verbs, powerful word partners, more complex structures however you can´t use it yourself.
So, if we forget 80% of what we learn the situation compels us to think of doing something about it. We should be exposed to these 80% again to retain 20% of it. Isn´t that right? The question is: language is very dynamic. The situations in life are very dynamic. How can you guarantee that you will be exposed to the same universe of words or expressions you keep forgetting, in a short time? We must take notes, obviously, so that you can study the notes many times until you retain them and put into practice what you have learned. However, the question is: if you are like most people you don´t bother to check your notes again, no matter the kind of training you are attending or attended.
You can develop you own way or registering and checking your notes afterwards but I would like to suggest something very simple and effective: 1- Open an Excel file and create a table with 3 columns: New input, Meaning and Example. Every very interesting word or expression you would like to learn, add to the “new input” column. Put the meaning in your own language or in the language you are learning and write an example on the third column. By writing an example you contextualize the word or expression and make it more “real” to your experience. This will help your brain to retain it. 2- Every now and again, open the file, cover on column and ask yourself the meaning or show the meaning asking for the word in the “new input” column. This way you will be creating a mechanism to be exposed to the words you keep forgetting. 3- Just by identifying the word or expression you want to add to your word bank you are already paying a different attention to it.
Fernando Reiff & Joel Barsky