defining clauses同non-defining clauses既句式係點?

The exact sense in which we use these terms is illustrated by the following groups, of which (i) contains defining clauses, (ii) non-defining.



The man who called yesterday left no address.
At the first meeting, which was held yesterday, the chair...
The function of a defining relative clause is to limit the application of the antecedent; where that is already precise, a defining clause is not wanted. The limitation can be effected in more than one way, according to the nature of the antecedent.
A non-defining clause gives independent comment, description, explanation, anything but limitation of the antecedent; it can always be rewritten either as a parenthesis or as a separate sentence, and this is true, however essential the clause may be to the point of the main statement.
To find, then, whether a clause defines or does not define, remove it, and see whether the statement of which it formed a part is unaltered: if not, the clause defines. This test can be applied without difficulty to all the examples given above.