最も有名なのがウーロン茶で : What is the usage of なの here?


What is the usage of `なの` in:

`最も有名なのがウーロン茶で`

To me, it seems to transfer a `adverb [有名]` to a `noun`, is that so? Could
someone help to explain, thx.

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**Update:**

To make the question more clear, the whole sentence is:

`日本で中国茶として最も有名なのがウーロン茶で、`




The predicative form of `有名` is `有名だ` and its attributive or adjectival form
is `有名な`. The `の` particle nominalizes (changes) the preceding adjective into
a noun.

So 最も有名な **`の`** がウーロン茶で

is saying that the most famous `thing` is oolong tea.

