Nonsense sentences with だ


I recently encountered these sentences which must be nonsense because AはBだ
means 'A is B'.

> 私は１０５号室だ
>
> 「ノルウェーの森」は村上春樹だ
>
> 東京は初めてだ




> ... which must be nonsense because AはBだ means 'A is B'.

It's not always appropriate to parse such sentences in this fashion.

The topic marker は does not always mark the **subject** of the sentence, the
substantive that is directly tied to the verb: sometimes it is instead marking
the **topic** , the outermost context of the current phrase. In 「私は１０５号室だ」,
the 「私」 is not the _subject_ , which would be directly tied to the copular
phrase 「１０５号室だ」, and instead this is the _topic_. A better translation (in
terms of better illustrating the meaning) might be:

> **私は** １０５号室だ  
>  → **As for me** , it is room 105.

What the "it" is in the English is context-dependent: perhaps the speaker has
been asked where they are, or where they think something is located, etc.

An example I've seen crop up multiple times is the sentence 「私はウナギです。」 If we
parse 「私」 as the **subject** , this becomes _" I am an eel."_ This might be
the correct interpretation -- but that would require a very specific context.
A more likely scenario is that the speaker is at a restaurant, and is either
ordering, or telling the server which dish is theirs -- in which case, the 「私」
is the **topic** , further distanced (grammatically, semantically) from the
verb, and a more correct translation would be _" As for me, it [my order] is
the eel."_ More idiomatically, _" For me, the eel"_, or even _" I've got / I'm
getting the eel."_

When evaluating sentences like 「AはBです」, consider whether it makes sense for
「A」 to be the **subject** , or the **topic**.

