However, as you will find out in a moment, high-level lexis is rarely about knowing one word, but being able to produce phrases that show a knowledge of collocation. What is collocation? It is knowing that certain words are used naturally together. Simple examples of this are the many verbs in English that collocate with either “make” or “do”. For example, we “do our homework” but we “make dinner“. There is no reason why these words collocate together – you just have to learn them.
A more advanced collocation would be knowing that we say “a wide gap” but “high cost” and “vast improvement” – in each of these phrases the adjective means “big”, but they collocate with different nouns. You cannot say “high gap” or “wide improvement” (but you can say “vast cost” and “vast gap”!!!!!).
Obviously, it is impossible for me to teach you every good collocation – my advice would be to find a good IELTS vocabulary book that is divided into topics, or study a CAE or CPE course. However, what I want to impress on you most is this: