Expanding the range of vocabulary is an undoubtedly daunting task when learning a new language, but Ebbinghaus's two discoveries can help you do it more efficiently. First, he found that we forget most of the information that we are trying to learn soon after we learn it. What it means is we always need to re-learn it again and again although we might feel like we have got everything after learning. Second, he found the so called edge effect which means we are likely to remember the first and the last items in a series best. According to this theory, focusing on the items in the middle rather than things on the edges is a clue when it comes to memorising things. To sum up, what we can do to memorise words efficiently is to go through what you learnt many times and to focus on items that are in the middle.