That Versus Which
One of my favorite writing conundrums, and one which I continually experience, is making the correct choice between 'that' and 'which.' A rule for choosing between these two seemingly alike choices requires the writer to decide if the clause, where it is used, is restrictive. A restrictive clause in a sentence restricts the clause's meaning to specific information. A non-restrictive clause can be left out of a sentence without changing the sentence's full meaning or intent. Another 'trick' for determining when to use 'that' and when to use 'which' is knowing whether your choice refers to something determinate or indeterminate. 'Which' will be used for an indeterminate clause and that clause is usually non-restrictive. Try removing the clause and see if any meaning is lost. If so, such a clause requires 'that.' Cautious writers find the difference.