Extending your vocabulary is of vital importance as you improve your English. First, teachers need to ensure that their students master a core vocabulary of around 2.000 words as the basis for all subsequent lexical development. The book explores the valuable work that has been done over the past century in identifying in a principled way just which words should constitute a basic core. It then shows, in a linguistically consistent way, through a rich selection of topical examples, how the basic core can be differentiated and expanded into related lexical items. And finally, noting that there are many school and university subjects that have to be studied in English, the book provides an advanced common core vocabulary of some 4.000 items which can embrace a wide range of academic, professional and personal interests.