I have read several definitions (e.g. here and here) and explanations (here for example), but I am not sure any real differences are drawn except one is 助詞, the other 名詞.

The list given for 形式名詞:

和語では「こと・もの・あいだ・うち・とおり・とき・せい・はず・かた・ほど・よし・ふし・ところ・ゆえ」など、漢語では「件・儀・体(てい)・方(ほう)・点・段・分」などがある。(精選版 日本国語大辞典)

The 準体助詞 list:


But there are cases where の can be used interchangeably with こと


In cases like this, is の a 準体助詞? 形式名詞? If の is a 準体助詞 while こと a 形式名詞, and they essentially serve the same grammatical purpose, doesn't that create some sort of paradox?

What about の in:



How exactly do 形式名詞 and 準体助詞 differ, given that both seem to refer to nominalizers?

1 Answer 1


Let me use these labels in this answer:

  • A: あれは彼だよ。(の as のもの)
  • B: 赤いが欲しい。こんなが欲しい。(の as もの)
  • C: 絵を描くが好きだ。(の as a nominalizer)
  • D: 彼女は学生なだ。彼は知っているだ。(explanatory-の)

準体助詞 is not really a widely used term. According to the following links, 準体助詞 can be roughly summarized as "a word which was originally a 助詞 but has gained the role as a (形式)名詞". Some people believe it's still a special 助詞, and some people believe it's effectively a (形式)名詞 (or a suffix) already.

  • 名詞 on Wikipedia says C is 準体助詞, and says it's called so because it was originally a 助詞.


  • 助詞 on Wikipedia says C is categorized as 格助詞 by some.


  • 準体助詞 on デジタル大辞泉 says A, B and C are 準体助詞. (But its definition contains ~とする, implying this is not a universally accepted concept.)


  • 準体助詞 on 精選版日本国語大辞典 says A is 準体助詞, but also says many believe it's just a noun.


  • and のだ on デジタル大辞泉 say A, B, C and D are all 準体助詞.

  • and のだ on 精選版日本国語大辞典 say A is "格助詞(準体助詞とする説もある)", B and C are just 名詞, and D is 格助詞.

  • の on 明鏡国語辞典第3版 explains A, B, C and D under 助詞, but without using the term 準体助詞 itself.

  • Many Wikipedia articles acknowledge C and D are 準体助詞. See these search results.

  • Several websites for JSL learners I checked treat の simply as a 形式名詞.

So all of A, B, C and D might be called (準体)助詞 depending on the writer's preference :)

I personally think の in B, C and D can be simply explained as a (形式)名詞. の in A is somewhat grammatically special, but it can be explained as a noun-forming suffix, too. Practically speaking, the etymology-based category, 準体助詞, seems not very useful to me. From the standpoint of a modern Japanese speaker, I can think of no practical merit in thiking 寝るのが好き and 寝ることが好き are syntactically different, even if this の was etymologically a genitive particle.

(By the way, I personally didn't know の-as-a-nominalizer derived from the genitive case particle の. It's semantically much closer to こと/もの now...)

  • One of my books treats a sentence like A as an omission of some item understood in the context. 私の友達の本です then becomes 私の友達のです. It treats の as a 助詞.
    – Nameless
    Feb 9, 2022 at 3:43
  • @Nameless Yes, that's what 精選版日本国語大辞典 says, too (修飾されるべき、下の実質名詞を省略したもの。準体助詞とする説もある).
    – naruto
    Feb 9, 2022 at 6:24
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    A potentially interesting addition is that A has a different pitch from B (though it only becomes observable when proceeded by a heiban word). For example, for A, わたしのだ{LHHHL}, but for B, こんなの{LHHL} and おなじの{LHHL}, even though all of わたし, こんな, and おなじ are heiban in usual contexts (i.e., わたしだ{LHHH}、こんなひと{LHHHH}、おなじひと{LHHHH}). So A is like の\, while B is more like \の. Feb 9, 2022 at 21:36
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    (For this reason I think of the surface の in A as the genitive, with the “もの” element that should be after it being deleted and only manifesting as a drop at the end, while B, C, D feel to me like generally the same sort of ”もの” meaning thing at varying levels of abstraction — so basically I agree.) Feb 10, 2022 at 2:22

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