What is the purpose of the が particle in this sentence?

Question

友だちがきれいな花をくれました。

I have translated this as: Friend gave (me) beautiful flowers.

I did not understand the usage of が , couldn't we have used は ? And in this case is my translation correct?

Answer 1

There are two possible reasons to use が instead of は here:

1. This 友だち has not been mentioned in the discourse yet. In other words, this sentence is "A friend of mine game me a flower" rather than "The friend game me a flower."
2. This ga is a neutral-description ga.
   • Can someone explain me the use of は and が in this sentence?
   • Why is this sentence ungrammatical? 「お寺が公園のとなりです。」
   • Why does 「電話は切れた」 sound more adversarial than 「電話が切れた」?

Saying 友だちはきれいな花をくれました is still grammatical, but the meaning would be a little different.