ABSTRACT
This chapter reviews the major theories and practices concerning the definition of idiom so as to provide the reader with a basic understanding of what scholars in general believe constitutes an idiom. It explores the perspective of second language learners on idiom definition. The chapter discusses the major approaches and systems that scholars have employed in classifying idioms. Idioms may be classified in many different ways, including, among others, Katz and Postal's division of lexical idioms and phrase idioms, Makkai's stratification-based dual system of idioms of encoding versus idioms of decoding, and lexemic idioms versus sememic idioms, Fernando's pure, semi-literal, and literal idioms, and Grant and Bauer's core idioms. Some of these classifications are primarily semantically based; others are, in essence, structurally motivated; some use both criteria; still others are functionally driven. Compared with Makkai's complex classification, Fernando's pure/non-literal, semi-literal, and literal idiom categorization appears much simpler.
