Synonymy has been one of the intriguing topics in lexical semantics. As a study of synonymy, this research explores and compares the meanings and uses of kotta and paluta ‘straight’ through an analysis of the Sejong Written Corpus. After a brief discussion of previous studies and dictionary definitions, this research shows the frequency rates and cooccurrence relations of kotta and paluta in the database. Examination shows that kotta occurs 71 times, and paluta 255 times, showing a great difference in the number of their occurrences in the database in spite of their similarity in meaning. Second, this research examines the cooccurrence relations of the two adjectives, showing that two thirds of the kotta tokens cooccur with concrete nouns, and that about three fourths of the paluta tokens with abstract nouns, showing a sharp contrast in the distribution. Based on the observation, this research explores metaphorically extended meanings of kotta and paluta in terms of the metaphors of MORALITY/ MANNERS/MIND... IS/ARE ENTITIES and MORALITY/INTEGRITY IS BEING STRAIGHT. Finally, this research shows that a corpus-linguistic approach and metaphor theory are useful tools for characterizing synonymous words and metaphorically extended meanings of synonymous lexical items.