Metaphor expresses the unfamiliar (known in literary jargon as the 'tenor') in terms of the familiar (the 'vehicle'). The tenor and the vehicle are normally unrelated: we must make an imaginative leap to recognise the resemblance to which a fresh metaphor alludes. In semiotic terms, a metaphor involves one signified acting as a signifier referring to a rather different signified. Metaphors initially seem unconventional because they apparently disregard 'literal' or denotative resemblance.