Eun Ha Hwang. 2014. The impact of lexical inferencing on expanding vocabulary: focusing on the size and depth of Korean loanwords. Yonsie University, Seoul, Korea. This study examines the validity to use Korean Loanwords for effective and efficient vocabulary expanding in KFL. Many studies agree with the importance of loanwords in vocabulary expanding with regard to its positive transfer from L1, which is English in this case, and learnability. Consequently, there are several researches focusing on Korean loanwords in effective Korean vocabulary teaching: presenting an essential loanword list for academic purpose, insisting on teaching a notational system of loanwords, and emphasizing cultural changed meanings of Korean loanwords for Korean learners. However, when it comes to the validity of using loanwords in KFL and KSL for rapid vocabulary expanding, it is very hard to find a research that attempt to prove it with empirical evidence. Therefore with the purpose of examining the validity of using Korean loanwords for expanding vocabulary knowledge from a receptive perspective, in this study, lexical inferencing using KFL learners’ L1 was encouraged. Participants went through a word list containing 223 Korean loan words from 'Vocabulary for Korean language education: basic and intermediate by The National Institute of the Korean Language'. The checklist using modified version of Vocabulary Knowledge Scale (VKS) was utilized to measure the learners' size and depth of vocabulary knowledge. Results indicate a notable progress after lexical inferencing in both beginner and intermediate learner's groups. Especially the beginner group took the most advantage of expanding their receptive loanwords knowledge when they tried to infer unkown loanwords from comparing the similarities between Korean loanwords and English, their L1. While lexical inferencing was effetive on most of the loanwords, some words, such as having sociocultural changes in their meanings, and new word formations, were difficult to presume with L1 knowledge. As a result, this study suggests an explicit loanwords teaching for efficient vocabulary expanding not only by using lexical inferencing but also by focusing on semantically changed loanwords.