Defining and non-defining

There are two kinds of relative clause: defining and non-defining. The first type usually does not have its own separate IP, the second does:

Version (i), defining, implies that I have more than one sister; I am singling out the particular one who lives in Canada; it is that sister I am talking about, not my other sister(s). Version (ii), non-defining, is consistent with my having only one sister; I throw additional information about where she lives.

(i) He â–¸used a comma that was 'wrong.
(ii) He â–¸used a 'comma, | which was 'wrong.
Here, version (i) has a defining relative clause (= the type of comma that was wrong). Version (ii) has non-defining relative clause, but is ambiguous: it may mean either 'he used a comma, and the comma was wrong' or 'he used a comma, and his using it was wrong' - i.e. the antecedent of the relative may be either the NP a comma or the whole clause he used a comma.

Defining relative clauses are much more frequent in conversation than non-defining ones. In typical cases such as the following, there is no intonation break before the defining relative clause:

â–¸Where's that 'pen I was using?
â–¸That's my 'coat you've taken!
There may well, however, be an intonation break after the relative clause, since the whole IP is now rather heavy:

This â–¸new 'car I've bought | has a â–¸special 'locking device.
The â–¸point you must re'member | is that ...

The distinction between defining and non-defining applies to certain other constructions as well:

â–¸Look at the house near the 'bus stop. (= not the other houses)
â–¸Look at that 'house, | near the 'bus stop.
â–¸Bicycles chained to the 'railings | will be re'moved.
â–¸Outside the 'courthouse | there were some 'bicycles | â–¸chained to the 'railings.
In particular, it applies to phrases in apposition.

(i) â–¸This is my colleague 'Charles.
(ii) â–¸This is my 'colleague, | 'Charles.
Version (i) identifies as Charles this particular one of my various colleagues. Version (ii) does not necessarily imply that I have only one colleague, but it does involve presenting the person's status (colleague) and name (Charles) as two separate pieces of information. There is also a third version, a single IP with Charles not accented.

â–¸This is my 'colleague, Charles.
Version (iii) offers two possibilities: either that Charles is a vocative, the name of the person I am speaking to; or that I have mentioned several people called Charles, and that this is my colleague Charles rather than, say, my cousin Charles.