Metaphor and Metonymy are two speech figures, more concretely, constitute word pictures.
A metaphor is a figure of speech that indicates two common semantic features between two concepts or ideas. Metaphor is very important in human communication. Seriously practically impossible to speak and think without resorting to metaphor. Recent research shows that during a conversation, humans use an average of 4 metaphors per minute. Ex: The moon is a cheese ball. In this case, the moon is characterized as a cheese ball because it has craters, just like some cheeses. Holes are then the common semantic feature between the two.
Metonymy, also a word figure, is related to a relationship of contiguity/proximity between two ideas or concepts. Ex: He drank the entire glass. In this case, the person does not drink the glass, but what was inside the glass.
In the linguistic sphere, metonymy has a significant function, in which the part is taken by the whole. Another example of this is a sail that represents a ship. The connection between ship and sail happens in the signifier, with each word the connection where metonymy is sustained is built.
Linguistically, the metaphor is verified between two signifiers, there being a substitution, where in the signifying chain one takes the place of the other.
Metaphor and Metonymy in Psychoanalysis
Jacques Lacan, French psychiatrist and psychoanalyst was responsible for introducing the concepts of metaphor and metonymy in psychoanalysis, and with that, these concepts went beyond a simple categorization of rhetoric. Jacques Lacan defines metaphor as a nonsense (non-sense) of the signifier chain, which results from the juxtaposition of signifiers. According to Lacan, metaphorical and metonymic processes are not separate.
Metaphor and metonymy are related to concepts developed by Freud, which are displacement and condensation, linked to the Interpretation of Dreams. Lacan related these concepts with metaphor and metonymy, thus making an analogy with linguistics. Later, Lacan links condensation with metaphor and displacement with metonymy. Through these two processes, it is possible to interpret unconscious desires, manifesting the subject's needs.
Meet some famous metaphors and see more Examples of Metaphors.
See also the meaning of definite and indefinite article.