Help me understand why these are predicate adjectives!

[aimeeteri]

Help! My son is learning about predicate nouns and predicate adjectives. I really thought I understood the difference, but I must not since I gave him incorrect direction on two questions. He had to identify if the last word in each of these sentences is a predicate noun or a predicate adjective. I believe they are predicate nouns, but his teacher says they are predicate adjectives.

But Ned's project was a disaster.
The evening sky was a spectacle.

Are "disaster" and "spectacle" really predicate adjectives? I just don't get it... please help explain it to me!

Thank you!!!

[susiedqq]

But Ned's project was a disaster.

This is a predicate adjective because "disaster" describes the main noun with the linking verb "was"

project / was / disaster

If it were a noun, it could replace (interchange with) the main noun.

But we can't say Ned's disaster was a project.

Sample of predicate noun:
Ned's project was a model car.

[aimeeteri]

Thank you! That is helpful. All of the examples I have found on predicate adjectives feature words that are always adjectives. The examples noted above are confusing because the predicate adjective could be a noun in another application. Your explanation about how you must be able to interchange the two words (subject and predicate noun) clarifies things. Much appreciated!

[riverkid]

That pesky little determiner 'a' leads me, no great grammar parser atall, to believe that these are predicate nouns. I can't think of any adjective that makes use of an article/determiner.

[susiedqq]

River - you are right!

But Ned's project was a disaster.
The evening sky was a spectacle.
These are predicate nouns.


Ned's project was disasterous.
The evening sky was spectacular.
These are predicate adjectives.

I hope I did not thoroughly confuse the original poster!