I know it's to indicate whether something is a Na adjective or not, but other
than the language rules stating it to be so, is there any real use of it?

I'm pretty sure everyone would understand you just fine with or without the
extra「だ」so to me it's really unnecessary from a practical standpoint.

Is there a linguistics standpoint that makes 「だ」absolutely essential and not
just a pointless language rule that everyone follow just because.
CC BY-SA 3.0
2017-12-09T07:20:43.767
55055
2017-12-13T14:42:24.147
22417
question
grammar usage nuances linguistics
Does using 「だ」in だと思う actually serve a practical purpose?
When と follows directly after a noun, it can be ambiguous if it stands for a
case particle or a quote. In addition, although it can be omitted in casual
conversation, it inevitably sounds a sentence with the verb omitted, hence not
authentic.
CC BY-SA 3.0
2017-12-09T14:06:14.993
55058
2017-12-09T14:06:14.993
4092
55055
answer
だ is a copula and it is a fundamental aspect of Japanese grammar and syntax -
[Copula](http://www.japaneseprofessor.com/lessons/beginning/the-copula-desu/)

Leaving it out would simply result in an ungrammatical sentence like
「そうと思う。」It's a bit like asking "Do you need the 'is' in "he is a man" in an
English sentence. You need it because in English the verb 'to be' functions as
a copula. People would certainly understand the sentence without the 'is',
right? But that's not how languages work. You need だ because the copula in
Japanese indicates the relationship of the subject and predicate.
CC BY-SA 3.0
2017-12-13T14:30:04.427
55147
2017-12-13T14:42:24.147
2017-12-13T14:42:24.147
25875
25875
55055
answer