Student or Learner
Are the two following sentences correct?
The house which I want to buy is on 5th avenue.
The house where I want to buy is on 5th avenue.
He suddenly quit his wife, which came as a shock.
1 - The house that I want to buy is on 5th Avenue.
2- The house, which I want to buy, is on 5th Avenue.
The first suggests that more than one house are being discussed. It answers the question: "Which house do you want to buy?"
In the second, only one house is being discussed. The phrase bracketed by commas gives additional information about that house, but does not change the meaning or sense of the rest of the sentence: The house is on 5th Avenue. (I want to buy it.)
In the first case, that is generally preferred. In the second, which is mandatory.