From what I know, ので differs to から grammatically because you add a な after な-adjectives for ので. For example:

その人は意地悪{いじわる}なので、嫌{きら}いです。- I do not like that person because they are mean.

But what would the past tense of this sentence be? Would it be:

その人は意地悪{いじわる}だったので、嫌{きら}いです。- I do not like that person because they WERE mean.

Is the な before ので necessary for past tense adjectives? I couldn't really find anything after googling. How does this work?


な is the attributive form of the copula だ (plain form of です). It is what だ becomes when that part of the sentence moves from the predicative position to form a relative clause (sometimes called an adjective clause because it functions like an adjective):

  • 部屋がきれいだ - The room is clean
  • きれいな部屋 - A clean room

There is no requirement for だ→な for sentences ending in verbs (not ending in だ) for the verb to form a relative clause. There is no need to insert a な here because だ was not there to become な. Inserting な would be grammatically wrong. The predicative form and the attributive form looks the same for verbs:

  • この手紙はペンで書いた - This letter was written by a pen
  • ペンで書いた手紙 - A pen-written letter

The past tense (or perfective aspect) of だ is だった. Even though だ→な when changing from predicative to attributive, だった remains as だった. There is no need to insert a な here either. Inserting な here would be grammatically wrong:

  • 部屋が静かだった - The room was quiet
  • 静かだった部屋 - The room that was quiet

What precedes ので has to end in attributive form:

  • Verb: するので
  • Verb(past): したので
  • i-adj: 高いので
  • i-adj(past): 高かったので
  • na-adj: 静かなので
  • na-adj(past): 静かだったので
  • noun: 学生なので
  • noun(past): 学生だったので

So finally in your sentence:

その人は意地悪だったので、嫌いです。 (☓)

There is no need to insert there since だった is already the correct form.

  • +1, but when you say "there is no need to ..." it admits the possibility that adding な might be permissible even if it is not needed. I think it would be safer to make clear that, not only is it not needed, it is not grammatical. Dec 31 '19 at 16:06
  • @user3856370 I can see how it might mean that. I wouldn't say that it admits that possibility. I'd say it does not preclude that possibility.
    – Flaw
    Dec 31 '19 at 16:12
  • I thought those two meanings were the same. Anyway, I'm not going to quibble over English in a Japanese language site :-) Dec 31 '19 at 16:18

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