The madrigal is polyphonic. (being polyphonic is characteristic of madrigrals)
Madrigals are polyphonic. (being polyphonic is normal for madrigrals)
A madrigal is polyphonic. (being polyphonic is required for madrigrals)
These are as opposed to
The madrigal is popular. (being popular is characteristic of madrigrals)
Madrigals are popular. (being popular is normal for madrigrals)
*A madrigal is popular. (being popular is required for madrigrals)
... and of course this last conclusion is wrong, producing the star.
Considering the explanations above, the bold part would be incorrect. Nevertheless, I cannot understand the bold parts well. I am really willing to get the red part as a rule of thumb for such a situation so that I could use the article A properly.
In a book it said:"the following is incorrect".
A computer has revolutionized publishing( being revolutionized publishing is required for computers)
My biggest question is only about the following. Would you please help me in a way so that I could use the function below for other situations like those above ?
being revolutionized publishing is required for computers)