Why is this sentence ungrammatical? 「お寺が公園のとなりです。」


I wrote this sentence (meaning "The temple is next to the park") in my
Japanese course and my teacher said it's wrong, because I was supposed to use
a は instead of a が.

My understanding is that there is always a が in a sentence, which may or may
not be visible/dropped (zero-ga pronoun) and the subject marked by が may or
may not be additionally marked with は. So I asked my teacher for
clarification, what the subject of that sentence is and why using が was wrong,
but the only explanation I got was "This sentence pattern uses a は", which
doesn't really start explaining anything.

I tried to clarify, if using が here is merely unnatural (and that is what my
teacher meant by "wrong") or actually grammatically incorrect, but my teacher
assured me, that using が is ungrammatical in that sentence.

Can someone elaborate as to why が is indeed ungrammatical in this sentence?
And if so, what is the subject of the sentence if not お寺?




In this case, が is incorrect because you are conveying a known piece of
information. When you describe a known or general fact about a subject (お寺),
you have to mark it with は, making it the **topic** of the sentence.

> お寺 **は** 公園の隣です。  
>  **The** temple is next to the park.  
>  (This is a known fact to you.)
>
> 鳥 **は** 飛べます。  
>  Birds can fly.  
>  (This is a general fact.)

Note that the subject of the first sentence is still お寺, but now it's marked
with は instead of が.

You have to use が when you firstly introduce something in the "universe of
discourse":

> お寺 **が** 公園の隣にあります。  
>  There is **a** temple next to the park.  
>  (As a response to something like "Is there a building related to Buddhism
> around here?")
>
> あの木の上に鳥 **が** います。  
>  There is **a** bird on that tree.  
>  (No one else has noticed this bird before this sentence.)

You have to use が when you report a **new** event or temporary status you have
just noticed regarding the thing marked with が. (neutral-description-が)

> お寺 **が** 燃えています！  
>  **The** temple is on fire!  
>  (The listener knows which temple you are talking about, but the information
> ('on fire') is something you just noticed.)
>
> 鳥 **が** 逃げました！  
>  **Our/The** bird flew away!  
>  (The listener knows which bird you are talking about, but the information
> is something new.)

In addition, there is something called exhaustive-listing-が. With this, you
are choosing and emphasizing something from several possibilities:

> お寺 **が** 公園の隣です。  
>  It's _the temple_ that is next to the park.  
>  (As a response to "So, what's next to the park is the post office, right?")
>
> 鳥 **が** 飛べます。  
>  _Birds_ can fly.  
>  (As a response to "Which vertebrate can fly?")

This is probably the only case where お寺が公園の隣です would make sense, but if this
is too difficult to you now, you can forget this and learn the easier ones
first.

* * *

> My understanding is that there is always a が in a sentence, which may or may
> not be visible/dropped (zero-ga pronoun) and the subject marked by が may or
> may not be additionally marked with は.

What do you mean by "the subject marked by が may or may not be additionally
marked with は"? You can think **は replaces が** when the subject is
topicalized, but you cannot mark a word with both が and は simultaneously. (は
can replace を, too.)

> using が here is merely unnatural (and that is what my teacher meant by
> "wrong") or actually grammatically incorrect

I would say it's grammatically incorrect (for your intended meaning). The
distinction of は and が is critically important in most cases. People may guess
what you are saying if you are lucky; in this specific case, people will
probably understand you, but they never fail to think "Oh, this person is
still bad at Japanese." If you are unlucky, it may end up with a severe
confusion ([example](https://japanese.stackexchange.com/q/57911/5010)).

Related (if some of my explanation didn't make sense, please read these
first):

  * [What's the difference between wa (は) and ga (が)?](https://japanese.stackexchange.com/q/22/5010)
  * [Can someone explain me the use of は and が in this sentence?](https://japanese.stackexchange.com/q/43213/5010)
  * [Why does 「電話は切れた」 sound more adversarial than 「電話が切れた」?](https://japanese.stackexchange.com/q/38639/5010)




In this case, が is incorrect because you are conveying a known piece of
information. When you describe a known or general fact about a subject (お寺),
you have to mark it with は, making it the **topic** of the sentence.

> お寺 **は** 公園の隣です。  
>  **The** temple is next to the park.  
>  (This is a known fact to you.)
>
> 鳥 **は** 飛べます。  
>  Birds can fly.  
>  (This is a general fact.)

Note that the subject of the first sentence is still お寺, but now it's marked
with は instead of が.

You have to use が when you firstly introduce something in the "universe of
discourse":

> お寺 **が** 公園の隣にあります。  
>  There is **a** temple next to the park.  
>  (As a response to something like "Is there a building related to Buddhism
> around here?")
>
> あの木の上に鳥 **が** います。  
>  There is **a** bird on that tree.  
>  (No one else has noticed this bird before this sentence.)

You have to use が when you report a **new** event or temporary status you have
just noticed regarding the thing marked with が. (neutral-description-が)

> お寺 **が** 燃えています！  
>  **The** temple is on fire!  
>  (The listener knows which temple you are talking about, but the information
> ('on fire') is something you just noticed.)
>
> 鳥 **が** 逃げました！  
>  **Our/The** bird flew away!  
>  (The listener knows which bird you are talking about, but the information
> is something new.)

In addition, there is something called exhaustive-listing-が. With this, you
are choosing and emphasizing something from several possibilities:

> お寺 **が** 公園の隣です。  
>  It's _the temple_ that is next to the park.  
>  (As a response to "So, what's next to the park is the post office, right?")
>
> 鳥 **が** 飛べます。  
>  _Birds_ can fly.  
>  (As a response to "Which vertebrate can fly?")

This is probably the only case where お寺が公園の隣です would make sense, but if this
is too difficult to you now, you can forget this and learn the easier ones
first.

* * *

> My understanding is that there is always a が in a sentence, which may or may
> not be visible/dropped (zero-ga pronoun) and the subject marked by が may or
> may not be additionally marked with は.

What do you mean by "the subject marked by が may or may not be additionally
marked with は"? You can think **は replaces が** when the subject is
topicalized, but you cannot mark a word with both が and は simultaneously. (は
can replace を, too.)

> using が here is merely unnatural (and that is what my teacher meant by
> "wrong") or actually grammatically incorrect

I would say it's grammatically incorrect (for your intended meaning). The
distinction of は and が is critically important in most cases. People may guess
what you are saying if you are lucky; in this specific case, people will
probably understand you, but they never fail to think "Oh, this person is
still bad at Japanese." If you are unlucky, it may end up with a severe
confusion ([example](https://japanese.stackexchange.com/q/57911/5010)).

Related (if some of my explanation didn't make sense, please read these
first):

  * [What's the difference between wa (は) and ga (が)?](https://japanese.stackexchange.com/q/22/5010)
  * [Can someone explain me the use of は and が in this sentence?](https://japanese.stackexchange.com/q/43213/5010)
  * [Why does 「電話は切れた」 sound more adversarial than 「電話が切れた」?](https://japanese.stackexchange.com/q/38639/5010)

