How many words do I need to know?
It has been estimated that a young English-speaking adult knows approximately 20,000 words (Coxhead, 2006:25)*, although, of course, this may vary greatly from person to person. However, you probably do not need the same range of vocabulary in English as a native speaker possesses. You simply need to know the words that you need to operate effectively in English. You need to know the words which will help you to study effectively at university. You certainly need to know the core 2,000 headwords of English that make up the basis of the language. You can see what these are by clicking here and going to Introduction and then the General Service list of The Using English for Academic Purposes website. You can also test yourself on these words by going to the website, The Compleat Lexical Tutor. Research has shown us that these words cover 80% of all text (Cobb 2008).
Obviously understanding 80% of a text is insufficient to give you a good understanding of it. Then, you also need to know the vocabulary of your subject area (maths, biology, logistics or maritime law, etc).
Finally, you also need to learn the vocabulary from the academic word list, because it occurs frequently in all academic texts. Research has show that if you do this you should be able to understand most academic texts within your subject area and you should be able to express yourself effectively when dealing with academic subjects (Cobb 2008).
So, to sum up, as a minimum, you need to know:
* Of course, this is only an average figure as knowledge of vocabulary obviously varies widely from person to person and how to estimate a person’s vocabulary is a disputed question. See How Many Words?