To this inglorious list belongs the third item in the list above: the idea that you can’t use which in a “restrictive” relative clause, one that crucially defines the word it refers back to. (A “non-restrictive” relative clause simply adds an extra bit of information.) Many people think that which can’t be used in sentences like the first one below; they think which can only be used in sentences of the second type. Restrictive: The car that I sold cost me $8,000. Non-restrictive: The car, which I sold, cost me $8,000.
