Page 126 - English for Writing Research Papers

108

6.10 Defining vs non-defining clauses: that vs which / who
Look at the two sentences below – in which case do I have more than one sister?
S1. My sister, who lives in Paris, is a researcher.
S2. My sister that lives in Paris is a researcher.

In S1 the information contained between the two commas is not essential. S1 tells
the reader that I have only one sister and she is a researcher – the fact that she lives
in Paris is just additional information. I could simply say: My sister is a researcher .

But in S2 I am giving very different information. I am telling you that I have more
than one sister, and that the sister that lives in Paris is a researcher. Perhaps my other
sister is a doctor and I am using Paris to distinguish between my two sisters.

This difference between who and that is the same as the difference between which
and that .

In scientific English, which and that have distinct uses. For example, imagine you
are instructed to do the following:

S3. *Correct the sentences below which contain grammatical mistakes.

Does S3 mean (i) that all the sentences contain grammatical mistakes, or (ii) that
you should correct only those sentences that contain mistakes? If all the sentences
contain mistakes, S3 should be rewritten as S4. If only some sentences contain mis-
takes, S3 should be rewritten as S5.

S4. Correct the sentences below, which contain grammatical mistakes.
S5. Correct the sentences below that contain grammatical mistakes.
The rule is that if you are simply adding extra information (S4) then use which

(things) or who (people) preceded by a comma (,). If you are defining the previous
noun then use that .
Given that not many people are aware of this distinction, it is probably better to
rewrite the sentences more explicitly. Thus S4 and S5, become S6 and S7,
respectively.
S6. Correct the sentences below, all of which contain grammatical mistakes.
S7. Correct only those sentences below that contain grammatical mistakes.