In the sentence, "母がすしを作ります。", why do we use が instead of は?


My book sentence: 母がすしを作ります。

[![img1](https://i.stack.imgur.com/rr7bpm.jpg)](https://i.stack.imgur.com/rr7bpm.jpg)

I consulted another book, which states:

> The case particle _ga_ can mark the subject of the sentence. However, when
> the subject noun is also treated as the topic of the sentence, being marked
> by _wa_ , _ga_ cannot be present. That is a part of the reason why the
> particle _wa_ often wrongly gives the impression of being the subject
> marker.

As I continued reading, from what I've understood, the context is
insufficient, there is none actually. In fact, I think that we can use either
particle for the following reasons:

  1. We can use が when we first introduce a item.
  2. We can use は when when the item was previously introduced or is already known.

How do we apply the above to the sentence? We may consider two cases:

  1. The speaker just told the listener that her mother will make sushi.
  2. The listener already knows the speaker has a mother.




Basically you can think 母 is always in "the universe of discourse", because
when you say 母, it's determined; it almost certainly refers to your own
mother. This means は is the ordinary particle choice. Usually, you should say
母はすしを作ります, replacing が with the topic-marker は.

However, が can be used in the following two cases:

  * When exhaustive-が is intended. 

> 母がすしを作ります。  
>  It's _my mother_ who makes sushi.  
>  (as a response to "Who makes sushi?")

  * When neutral-description-が is intended. 

> 母がすしを作ります。  
>  (I just noticed) my mother will make sushi!  
>  (when you are told to report everything happening in your house)

I think your textbook will soon explain these special usages of が, but you can
read several previous questions:

  * [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 is this sentence ungrammatical? 「お寺が公園のとなりです。」](https://japanese.stackexchange.com/q/68923/5010)
  * [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)

Either way, if there is no previous context at all, 母がすしを作ります sounds unnatural
and sudden. But textbooks sometimes need to show you this kind of "un-
topicalized" sentence to explain how the Japanese sentence is structured.




Basically you can think 母 is always in "the universe of discourse", because
when you say 母, it's determined; it almost certainly refers to your own
mother. This means は is the ordinary particle choice. Usually, you should say
母はすしを作ります, replacing が with the topic-marker は.

However, が can be used in the following two cases:

  * When exhaustive-が is intended. 

> 母がすしを作ります。  
>  It's _my mother_ who makes sushi.  
>  (as a response to "Who makes sushi?")

  * When neutral-description-が is intended. 

> 母がすしを作ります。  
>  (I just noticed) my mother will make sushi!  
>  (when you are told to report everything happening in your house)

I think your textbook will soon explain these special usages of が, but you can
read several previous questions:

  * [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 is this sentence ungrammatical? 「お寺が公園のとなりです。」](https://japanese.stackexchange.com/q/68923/5010)
  * [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)

Either way, if there is no previous context at all, 母がすしを作ります sounds unnatural
and sudden. But textbooks sometimes need to show you this kind of "un-
topicalized" sentence to explain how the Japanese sentence is structured.

