It was such a lovely party.

[lmd]

Why do we say "it was such a lovely party" and not "it was such the lovely party"? ie why do we use the indefinite article when we are talking about a specific party? What is the rule here?
Thanks in advance!

 

[Tarheel]

Why do we say "it was such a lovely party" and not "it was such the lovely party"? ie why do we use the indefinite article when we are talking about a specific party? What is the rule here?
[...........]

Gee, I've never thought about that one before. I guess the person is thinking it (the party) was an enjoyable/fun/lovely party.

 

[jutfrank]

The pronoun 'it' refers specifically to the party but the noun phrase 'a lovely party' refers to a general kind. It's like saying 'that specific party was one particular case of what can generally be classed as 'a lovely party''.