FIGURES OF CONTIGUITY
Different in kind from the simile and the metaphor are the tropes classed as figures under the names, synecdoche and metonymy. In the case of figures of similarity the shift of names is between things of different classes but associated on account of likeness. In the case of synecdoche and metonymy the shift of names is between things associated by actual contiguity, either physical contact, or contact in various thought relations.
The simplest case is that of synecdoche, where the name of the part is applied to the whole, or that of the species to the genus, or that of an individual to a general class, or, less frequently, one of these shifts is reversed. Instances are familiar enough in common use, in such expressions as: 'all hands aboard,' 'a fleet of fifty sail,' and uses of words such as wheel for bicycle, Nimrod for hunter, motor for motor car, or the slang hard tails for mules. The shift in the reverse direction appears in engine for locomotive, corn for maize (Indian corn), provisions for food, disease for malady, revolution for change in government, cattle for cows, currency for money, etc. This latter kind of shift will receive more detailed discussion in the following chapter, under the head of specialization.
Under the head of metonymy are included a number of shifts of wide variety, due to association in a wide variety of relations: that of cause and effect, in tongue for language; that of material and product, in copper or nickel for small coins, cold steel for bayonet; that of sign and thing signified, in gray hairs for age, bloodshed for destruction of