If we were to make a list of the areas of linguistic knowledge a learner needs to be competent in - eg syntax, lexis, collocation, phraseology, pragmatics, discourse knowledge, world knowledge - then 'metonymy' (the relationships, especially part-whole, between closely-related concepts/words/ things) is unlikely to be amongst them. This talk makes a case for metonymy as a vitally important resource in conceptualization and communication, and argues that the language learner who is made aware of this phenomenon is at an advantage.
Metonymy is important in many ways: it is involved in understanding word categories eg, synonyms, hyponyms, prototypes and sense vs reference; it plays a vital role in naming individual entities and complex social practices by selecting a single salient feature; it is the mechanism behind the process of 'narrowing' involved in understanding literal language and 'highlighting/hiding' in metaphoric language; it is used in discourse to give an 'ultra-realistic' register and to persuade by exemplification.
Roman Jakobson saw communication progressing along one of two paths, the metaphoric or the metonymic (Jakobson 1956). Metaphor has been the focus of intense scholarly activity as a result of Lakoff and Johnson's pioneering work (Lakoff & Johnson 1980, 1999) and now Metaphor Studies is a discipline in its own right. Metonymy, however, has received much less notice, perhaps because it is less obvious, less colourful and easier to overlook. As a consequence, this hugely important source of linguistic expression has been under-exploited in training language teachers, although, being concerned with 'relatedness', it is a resource which is readily to hand, already within the learner's grasp.