The purpose of this study is to examine syntactic, semantic, and pragmatic features of the two typical and basic ‘gratitude’ expressions of the Korean language, kamsahapnita and komapsupnita, and then investigate linguistically significant differences between these two expressions. For this purpose, authentic data have been collected and analyzed in terms of linguistic concepts. A general assumption about kamsahapnita and komapsupnita among both native and nonnative speakers of Korean is that these two expressions are simply interchangeable, the only difference, if any, being that kamsahapnita is more formal and polite than komapsupnita. This study, however, found that such an pragmatic/stylistic approach to the choice between the two expressions of ‘gratitude’ is far from being sufficient in accounting for the acceptability of each of the two expressions. The data collected for this study showed morphological, syntactic, and semantic differences between the two expressions, kamsahata and komapta. The study findings are the following: (1) kamsahapnita is an dynamic/event verb, whereas komapsupnita is a stative, psyche adjective; and (2) komapsupnita has Theme or Experiencer as the subject, whereas kamsahapnita has Agent as the subject. Thus, the choice between the two expressions of ‘gratitude’ is determined by linguistic competence, implicit or explicit, rather than by pragmatic competence. These findings are expected to contribute to the achievement of adult KSL/KFL learners, who are mostly known to benefit more from explicit knowledge than from implicit knowledge about the target language.