I wrote the following sentence in a post
"art form" is the most common phrase.
In fact, I constructed it as the following version first and then changed it as the one above.
"art form" is the most common.
The abandoned version doesn't have the noun "phrase" at the end of it.
A native speaker told me that it was incomplete but she didn't explain why is that.
I seems that the pattern
noun + be + adj is incomplete, which might not be true in general.
Is it because the sentence uses the superlative form?