Raise Your English Level with More Vocabulary
Some studies have shown that for learners to fully understand a written work, they need to know 95 percent or more of the words in it. That means that if there are only five or more words you do not know in a 100-word text, you might not really understand it!
Source : https://learningenglish.voanews.com/a/raise-your-english-level-with-more-vocabulary/7148252.html