Tense of sentences ending with のだ such as 楽しかったんだ


From what I can find,

> 楽しかったんだ

is considered to be in the past tense, which confuses me.

I would have thought that の nominalized the preceding phrase, and the
sentences as a whole was then placed in the present positive by the copula だ
predicating the main clause.




楽しかったんだ is indeed `楽しい + た (past) + の (explanatory-no) + だ (copula)`. The のだ
part can be translated into English as "It's that ～", "The thing is ～", "I
mean ～", "You know, ～", "I tell you, ～" or whatever, but this part itself is
in the present tense because it's about the _current_ mood of the speaker. The
past marker (た) is attached to 楽しい, but technically speaking, it's "wrapped"
in a subordinate clause.

So, is this sentence in the past tense or present tense? **It depends** on
what aspect of the sentence interests you. If you're interested in pure
syntax, the main predicate of this sentence, (ん)だ, is undoubtedly in the
present tense. However, if you consider the main focus of the sentence is
楽しかった ("it _was_ fun"), and view のだ as an added nuance to convey the speaker's
mood, then it would be perfectly accurate to describe the sentence as one
about the past. The fun experience definitely happened in the past, after all.

If you ask English speakers whether the sentence "I tell you, it was fun!" is
in the present or the past tense, you would likely get a variety of responses,
wouldn't you? Some might say the sentence is in the past tense because "I tell
you" is just a set phrase that expresses a mood, like "hey". Your question is
the same.

* * *

If you move the past marker (た) to the end of the sentence, you'll get
楽しいんだった, which is `楽しい + の (explanatory-no) + だ (copula) + た (modal-ta)`. This
is still grammatical but means something you might not expect: [Conjugated
word + んだ vs nonconjugated word + conjugated
んだ](https://japanese.stackexchange.com/q/60788/5010)




楽しかったんだ is indeed `楽しい + た (past) + の (explanatory-no) + だ (copula)`. The のだ
part can be translated into English as "It's that ～", "The thing is ～", "I
mean ～", "You know, ～", "I tell you, ～" or whatever, but this part itself is
in the present tense because it's about the _current_ mood of the speaker. The
past marker (た) is attached to 楽しい, but technically speaking, it's "wrapped"
in a subordinate clause.

So, is this sentence in the past tense or present tense? **It depends** on
what aspect of the sentence interests you. If you're interested in pure
syntax, the main predicate of this sentence, (ん)だ, is undoubtedly in the
present tense. However, if you consider the main focus of the sentence is
楽しかった ("it _was_ fun"), and view のだ as an added nuance to convey the speaker's
mood, then it would be perfectly accurate to describe the sentence as one
about the past. The fun experience definitely happened in the past, after all.

If you ask English speakers whether the sentence "I tell you, it was fun!" is
in the present or the past tense, you would likely get a variety of responses,
wouldn't you? Some might say the sentence is in the past tense because "I tell
you" is just a set phrase that expresses a mood, like "hey". Your question is
the same.

* * *

If you move the past marker (た) to the end of the sentence, you'll get
楽しいんだった, which is `楽しい + の (explanatory-no) + だ (copula) + た (modal-ta)`. This
is still grammatical but means something you might not expect: [Conjugated
word + んだ vs nonconjugated word + conjugated
んだ](https://japanese.stackexchange.com/q/60788/5010)

