Much has been said and written about the usage of these two words and I could
spend paragraphs in explanation. However, for most purposes the following
illustration should suffice. I'll refer you to Fowler or your favourite
grammarian for a more detailed exposition.
'That' is used in a restrictive sense; i.e. it identifies one object
among many, pointing out the item that has a specific characteristic. So, 'A mini-skirt
that is short…' tells the reader that you are referring to the one skirt,
amongst the many, that is notable because of its lack of length. It's probably
worth pointing out here that there is no comma dividing the object from the
'Which', however, is used in a non-restrictive way; i.e. it points to a
single item possessing the specified quality. So, 'A mini-skirt, which is
short…' tells the reader that the skirt is short, without comparing it to any
other. Note also that the object and its description are separated by a comma.
So, to enlarge on the examples in a way that will hopefully illustrate
the point more fully:
'A mini-skirt that is short is bound to draw more male eyes than a
mini-skirt of normal length.'
'A mini-skirt, which is always short, will cover very little of the
In the first example, if the words 'that is short' are excluded the
sentence has a different meaning. The restrictive clause 'that is short' is
crucial to the real meaning of the sentence.
But, in the second example, if the words 'which is always short' are
missed out, the sentence means the same thing. The non-restrictive clause
'which is always short' merely adds a bit of information to the sentence
without altering its meaning.
Probably, therefore, the easiest
way to remember when to use 'that and when 'which' is more appropriate, is to
decide whether you could ditch the clause. You can ditch the 'which' but lose
the 'that' and you'll look a prat.
27 September 1988 I
married my wonderful wife, Valerie. We've been very happy ever since.
27 September 1981 The
first TGV high speed train journey took place in France.