の: nominalization vs. 'the one that...'


の can be used as a noun with a relative clause in what appears to be two
separate situations.

  1. Referring to a thing or person, e.g. '来たのは田中です。' ('The one who came is Tanaka.')

  2. Nominalizing a verb (as does こと), e.g. '田中が来たのを見た。' ('I saw that Tanaka came.') This can be interpreted as 'the fact that...' or 'the event that...'. (This is probably what gave rise to のに and ので.)

How close are these grammatically and historically? For instance, two
instances of the same bit of grammar, or superficially similar but really
coming from quite different places?




I think you're getting confused by the differences in the English
translations. The function of nominalizing の in both of your examples is
identical: it nominalizes the preceding verbal phrase.

English requires various coordinating pieces to connect phrases, things like
"that" and "the one who". The の works a bit like these coordinating pieces in
English.

This use of の might become more clear by mixing things up a bit and generating
more examples.

  * 来たのは田中です。 
    * Came `[NOM]` `[TOP]` Tanaka `[COPULA]` → The came is Tanaka → The one who came is Tanaka
  * 田中が来たのを見た。 
    * Tanaka `[SUB]` came `[NOM]` `[OBJ]` saw → `[I]` saw `[that]` Tanaka came
  * 遅く来たのは問題なかった。 
    * Late came `[NOM]` `[TOP]` problem wasn't → It wasn't a problem `[that]` `[someone]` came late
  * アプリを開かずに通知が来たのが分かるように設定する 
    * Application `[OBJ]` not opening `[INSTRUMENTAL]` notification `[SUB]` came `[NOM]` `[SUB]` understand way `[INSTRUMENTAL]` setting do → Configuring `[so that]` `[you]` know `[that]` a notification has come without opening the application

