Abstract
Considering the wealth of research on second and foreign language vocabulary learning, it is well established and documented that vocabulary knowledge is dynamic and incremental in nature. While some aspects of vocabulary knowledge might be mastered in a short period of time, others need a long time to be established, and longitudinal research could provide insights into precisely how language learners approach vocabulary learning, both within and beyond the classroom. The present article reviews the recent literature on the development of vocabulary knowledge, drawing on the three major types of vocabulary knowledge: breadth (how many words of the target language learners know), depth (what the learners know about the target words) and degree of mastery of receptive and productive vocabulary knowledge. The findings reported in these studies revealed that the process of acquiring vocabulary knowledge is not only complicated but that multiple knowledge dimensions are gradually learned and sooner than others.