    Sentence 1: Perhaps the Proximity people  thought that they had got round that little  problem by giving the same definition for each of  the items in the list; but we know that only very  rarely are two synonyms bi-unique (which is  another way of saying that if A = B, B does not  necessarily always equal A), an ineluctable fact of  language.    Sentence 2: Synonyms are very common in  English.