The is the commonest word in English. This word is also known as one of the most difficult grammatical items for Korean learners of English as a foreign language. This paper focuses on the non-generic use of the English definite article, and examines the grammatical descriptions of the article in Advanced English Grammar and English Grammar in Use. It reveals that some of the important usages of the definite article are not included in 'the grammar books', and observes, following Park and Song (2001), that these unlisted usages cause much difficulty for Korean learners to improve accuracy in the article use. Underscoring the organic view of language, the paper proposes that a comprehensive and systematic understanding of 'grammar' is prerequisite for optimum efficiency in teaching the English definite article to Korean EFL learners.