「昨日ここへ来たのはだれですか」Is の short for 者?

Question

昨日ここへ来たのはだれですか

Book translation: who is the one who came here yesterday?

My understanding is the following: 「昨日ここへ来た」 is a relative clause modifying the pronoun 「の」 to mean "the one who came here yesterday", then は marks it as the topic. Because the interrogative word だれ is used, "the one" must be a person, so we use "who".

Now, can we replace 「の」 with 「者」? If so, would it be redundant because 「だれ」 is used?

昨日ここへ来た者はだれですか

Answer 1

Syntactically, this の is a noun, and everything before it is a relative clause. But I think it's best to treat this の as "some special noun working as a placeholder". It's also different from what we usually call a nominalizer (which turns 見る "see" to 見るの "seeing", etc.).

Your sentence is a cleft sentence, a special construction to focus a certain part of a sentence. This の roughly corresponds to the "placeholder it" in English cleft sentences like "It's John who ate the cake". You can see that this it is specially referring to a person, which is odd outside of this construction. Likewise, の in a cleft sentence is a special noun which is used in place of many things including 者/人, 物, 場所/所 and 時/時間, and it is unlikely to be an abbreviation of any particular word.

• 昨日ここへ来たのはだれですか？
  昨日ここへ来た人はだれですか？
  Who was it that came here yesterday?
  _{(This can be rephrased as "Who was the person who came here yesterday?", but that does not mean this it is short for person.)}
• 彼がここへ来たのはいつですか？
  彼がここへ来た時間はいつですか？
  When was it that he came here?
• 昨日彼が来たのはどこですか？
  昨日彼が来た場所はどこですか？
  Where was it that he came yesterday?
• 昨日彼がここへ来たのは何故ですか？
  Why was it that he came here yesterday?
  _{(For this one, I don't know how to rewrite this using a normal noun and a normal relative clause)}