The relation between thinking and speaking tends to be thought and theorized in causal terms: speakers express what they have thought or are thinking. That is, speech is theorized as a copy of thought even though thought itself may be theorized in terms of inner speech. The verb "to express' – as a live or dead metaphor – indeed portrays this relation as one in which some content of a container is pressed out. The verb etymologically derives from the Latin ex-, out + pressāre, to press, to squeeze.