Sentences may contain the same proposition and still be different. As an evident case, a sentence in English and its equivalent in Polish are two different sentences containing the same proposition. A sentence may also contain elements which do not form part of the proposition: “Adam is still waiting for Roz” contains the same proposition as the same sentence without still. Finally, the same proposition can be expressed by different grammatical forms of different words: “The man patted the dog” and “The dog was patted by the man” contain the same proposition. What we usually produce is not sentences (unless we are in a language class, for instance) but utterances, i.e. instantations of sentences. The sentence “We’ve bought a new car” does not refer to any new car. Speakers use it to refer to a car. The same sentence produced by me this year and twenty years ago or produced by my neighbour refers to different cars. So strictly speaking, linguistics expressions do not by themselves refer, they can only be used by speakers to refer. (Siewierska, Anna: “Semantics”, in: Culpeper, Jonathan, Katamba, Francis, et. al. (eds): English Language. Basingstoke: Palgrave Macmillan, 2009: 188-201)