How "Noun + Adj + Adj + 的" (reduplication of adjectives) is grammatically equivalent to "Noun + (Adv of degree) + Adj"? This question is motivated from Why 的 in reduplication of adjectives &quot;Noun + Adj + Adj + 的&quot;?. In the answers, it was argued that the reduplication of adjectives structure:



Noun + Adj + Adj + 的
Ex: 他的儿子高高的。



is indeed a topic - comment structure:

Noun - Adj + Adj + 的
Ex: 他的儿子 - 高高的。

with a meaning (approximately) equal to:



Noun + (Adv of degree) + Adj
Ex: 他的儿子很高。
Ex: His son is tall.



From the previous post, @dan:

There is no grammar difference between 你的脸很红 [structure 2.] and 你的脸红红的 [structure 1.]. 红红的 acts the same as 很红.

I don't understand how 1. and 2. are grammatically equivalent. I believe:



is a complete sentence: the Noun (他的儿子) is the subject, the (Adv of degree) + Adj (很高) is the predicate and the Adj (高), the adjectival verb.




is only a noun phrase, without Verb and Predicate. We can see it because the topic - comment structure makes it equivalent to:


Adj + Adj + 的 + Noun
Ex: 他的高高的儿子。



Where I am wrong in 1.? How can Adj + Adj + 的 work as a predicate with a verb?

A few examples of the grammatical equivalence of both structures:

这只小猫毛长长的，白白的，非常漂亮。
The hair of this small cat is long, white and extremely pretty.

Here, 长长的 and 白白的 are grammatically equivalent to 非常漂亮.

这个孩子的眼睛大大的，和她的妈妈一样。
This kid's eyes are big, just like his mother.

Here, 这个孩子的眼睛大大的 is translated to the complete sentence This kid's eyes are big.
How “Noun + Adj + Adj + 的” (reduplication of adjectives) is grammatically equivalent to “Noun + (Adv of degree) + Adj”?

[Noun + Adj X2 + 的] = [Noun + degree adv + adj]

Both are 'topic-comment' sentence

[Adj X2 + 的] functions the same as [degree adv + adj] in this case (a noun at the beginning but no noun at the end)