Synecdoche. A word is used for some larger whole of which that which it refers to is a part; for example, 'strings', 'roof', 'bite' in At this point the strings take over [stringed instruments] They all live under one roof [in one house] Let’s go and have a bite [have a meal] These are generally thought of as lexical, or lexicosemantic, processes, with synecdoche being based on meronymy, and metaphor and metonymy on kinds of synonymic relationship. Alternatively, we can interpret them grammatically, in terms of the relational processes [...] Synecdoche derives from possessive (ʻhasʼ) type; in the special sense that a whole ʻhasʼ its part: violins have strings a house has a roof a meal consists of bites Thus metaphor, metonymy and synecdoche are forms of lexical variation stemming from the three fundamental semantic relationships of elaboration, extension and enhancement [...].
- Halliday (1985), a pag.320