The purposes of this study are to clarify features of Korean adverb tel ‘less’ and to apply the result to Korean education as a foreign language. Korean learner’s corpus and Native speakers of Korean’s corpus were used to examine the frequencies of tel ‘less’ and the co-occurrence relation between adverb tel ‘less’ and predicates. The Korean adverb tel ‘less’ is usually studied at the lower level in Korean language learning; however, Korean learners have difficulty in using it because of its properties. The frequency of using tel ‘less’ in learner’s corpus was mush fewer than the frequency of using tel ‘less’ in corpus of native Korean speaker, and there were even many errors. In the corpus from native speakers of Korean, adverb tel ‘less’ was always used in comparative sentences, but the usage of tel ‘less’ was changed by characteristic of predicates in comparative sentences. If the adverb tel ‘less’ can be used with poda(보다) ‘than’, tel ‘less’ was used to compare degree of the predicate, which a subject of the sentence had, with another or other things had. However, if the adverb tel ‘less’ cannot be used with poda ‘than’, it was used to compare the degree of predicate itself. Thus, the adverb tel ‘less’ cannot be used when it cannot compare the degree of predicate. I extracted predicates which are frequently used with the adverb tel ‘less’ and presented a way of teaching the adverb tel ‘less’. It would be helpful to apply the properties of adverb tel ‘less’ and the teaching method of it to Korean learners. (Hankuk University of Foreign Studies)