What is the exact meaning of "Xのは"?


I just came across this sentence:

> 日本語を上手に話すのは難しい。

While I do understand the meaning overall, I am confused as for why it's 話すのは
instead of 話すは. If anybody could explain what のは means, that'd be really
helpful!




In this case の is a nominalizer. Basically turns the sentence it precedes into
a noun equivalent.

In your example, basically the の turns the part before into "the (thing of)
speaking Japanese well" and the part after is just "is difficult". The は in
between is just the usual topic particle は (the topic being the whole thing of
speaking Japanese well).

You can do so also with other particles, not just は. For example:

> のは＝の＋は
>
> <日本語> は むずかしいです。 Japanese is difficult. <日本語を話すの>は むずかしいです。To speak Japanese
> is difficult.
>
> のが＝の＋が
>
> <勉強>が好きです。 I like studying. <日本語を勉強するの> が好きです。 I like to study Japanese.
>
> のを＝の+を
>
> <たばこ>を やめます。 I quit smoking. <会社でたばこをすうの>を やめます。 I quit smoking in the
> office.

The examples above are taken from
[here](https://www.italki.com/question/139295). Also I just found a possibly
related question here [on this
website](https://japanese.stackexchange.com/questions/1322/what-is-the-
difference-between-%E3%81%AF-and-%E3%81%AE%E3%81%AF).

