Introduction

Although there is a long history of research on words, the vast majority of studies of vocabulary have appeared over the last thirty years. Because vocabulary plays a role in most aspects of language development, studies of vocabulary may be more common than studies of any other area of applied linguistics and the amount of research is increasing. In 2013 Nation reported that approximately 30 per cent of the research on vocabulary had been published since the publication of his seminal text on teaching and learning vocabulary in 2001. Essential to understanding and evaluating vocabulary studies is awareness of the core issues related to learning words.