One of the most interesting aspects of the English language is the ability to change the order of words and still end up with the same meaning such as 'John bought a book' and 'A book was bought by John'.You may recognise these as the active and the passive forms of a sentence, the passive sentence being the one where the object is given more emphasis than the subject as opposed to the standard subject-verb-object. But if we can easily shift the object and subject around, how do we recognise which one is which in any given sentence