Page 127 - English for Writing Research Papers

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S1 and S4 are grammatically known as non-defining clauses. In a non-defi ning rela-
tive clause you add extra information. You could remove the clause and the resulting

sentence would still make sense. In non-defining clauses which (for things) and who
(for people) are used.

S2 and S5 are examples of defining clauses, also known as restrictive clauses. They
give essential information without which the sentence would make no sense. In

defining clauses, only that can be used.
Here is another ambiguous example:

S8. *The table below gives details of the parameters which are not self-explanatory.

The reader does not know if the writer

• has forgotten to put a comma after parameters and thus means that none of the
parameters are self explanatory
• should have put that instead of which and thus means that the table only gives
details of those parameters that need to be explained

A similar problem arises when the author does not use either which or that , as in S9.
S9 would not be considered correct English by most language experts.

S9. *This is followed by a characterization of the states poorly represented at atmospheric
pressure.

S9 can be disambiguated as in S10 (non-defining) and S11 (defi ning).

S10. This is followed by a characterization of the states, which are poorly represented at
atmospheric pressure.
S11. This is followed by a characterization of all those states that are poorly represented at
atmospheric pressure.

Note: In spoken English, people do not usually make such a distinction and may
simply use which for things, and who for people, irrespective of whether they are
using defining or non-defi ning clauses.