definite article: the

[Winwin2011]

We use "the" in the following sentences:

1. What's the matter?
2. What's the purpose of your visit?

When I went to the following website, it seems that I couldn't find the rule apply to the above sentences.

English Grammar | LearnEnglish | British Council | definite article: the

Could anybody help, please?

 

[5jj]

There is only one of these things.

The 'matter' in #1 is the problem/difficulty that the addressee seems to be facing.
The 'purpose' is defined in #2

 

[Winwin2011]

There is only one of these things.

The 'matter' in #1 is the problem/difficulty that the addressee seems to be facing.
The 'purpose' is defined in #2

Thanks, 5jj.

I'm sorry I still don't understand.Do you mean "1. What's the matter? 2. What's the purpose of your visit?" apply to the following rule?

We use the definite article in front of a noun when we believe the hearer/reader knows exactly what we are referring to.
• because there is only one:

What do you mean for the following?

The 'matter' in #1 is the problem/difficulty that the addressee seems to be facing.
The 'purpose' is defined in #2

 

[5jj]

The 'matter' in #1 is the particular problem/difficulty that the addressee seems to be facing. No other 'matter' is involved; There is only one.

The 'purpose' is defined as that of your visit. No other problem is involved; There is only one.