1. The vertical axis of communication in neurosis linguistics and semiotics. The horizontal axis or syntagm defines the deep structure of a particular piece of communication, with the vertical axis specifying the possible lexical variations that structure can meaningfully accommodate. So in the sentence âthe boy went to the shopâ, we can substitute girl for boy, beach for shop and so on, all without altering the âa person went somewhereâ relational structure of the sentence. 2. American historian of science Kuhn, Thomas Samuel uses this term to describe different moments in scientific development, coining the phrase âparadigm shiftâ to name the ruptures that occur in thought when a new discovery is made. The best known example of so-called âparadigm shiftâ is of course the Copernican revolution, namely the insight that the earth is not the centre of the solar system.