What does 'a beautiful fish' mean?

I saw a beautiful fish in the street market the other day. It was orange and blue. I'm thinking of buying some next Sunday.

How would native speakers feel about these two sentences? One of my friends said that a beautiful fish in this sentence doesn't mean 'one beautiful fish' but means 'a type of beautiful fish'. Can you tell me what the phrase means?

I imagine that the speaker was referring to a fish that she was considering putting into her aquarium rather than her stomach. She saw one fish that she thought was beautiful.

Here, a beautiful fish is referring to a fish which looks good - it is fresh and has good coloration. This fish is not stale, but seems to be in prime condition for cooking.

I would say that it is impossible to tell:

1) If the fish was alive or dead
2) If it was just one individual fish or a type of fish.

Or even whether the intention was to eat it or put it in a tank.

Thank you all so much for your help.

Then are the two original sentences all right grammatically, only they are ambiguous?
And when we say 'I saw a young man/a big dog/ a thick book there', these underlined phrases could mean 'a type of young man/big dog/thick book', not just an individual man/dog/book?

joham said:

Thank you all so much for your help.

Then are the two original sentences all right grammatically, only they are ambiguous?
And when we say 'I saw a young man/a big dog/ a thick book there', these underlined phrases could mean 'a type of young man/big dog/thick book', not just an individual man/dog/book?

Click to expand...

"I saw a beautiful fish in the street market the other day. It was orange and blue. I'm thinking of buying some next Sunday."
The sentences above are grammatical, taken as a whole their meaning is ambiguous. "I saw a young man" means what it says, you saw a man somewhere, he was young.

If you saw a dog you saw a real, actual, physical dog. The dog is necessarily one type of dog, but that is not the main idea expressed in the simple sentence "I saw a dog."

If you say "I saw a dog today that was so cute. I'd like to have one like that," then you have segued from talking about the particular dog you saw to generalizing about that type of dog.