I started to learn Japanese grammar yesterday,so I am kinda of new to this. My question is this: in an example in my textbook it says :

Sushi wa tabeta.
I ate sushi. (Literally: As for sushi, I ate it.)

Can I just use "ga" instead of "wa"? When should I use "ga","o" and "wa"?



Would mean that it is the すし that does the action of 食べる. So for this sentence you cannot use が.


As your textbook says, it means "I ate sushi. (Literally: As for sushi, I ate it.)" and it gives a nuance of contrast: "As for the sushi, I ate it (, but I did not eat the other food)".


Is the most neutral way to say "I ate sushi".

If you get asked the question 何を食べましたか。 (what did you eat?), however, you can only reply by using を (すしを食べました) and not は. The reason for this is that the question is neutral, so answering it with a sentence that shows a nuance of contrast such as すしは食べた。 would make it quite unnatural.

That being said, if you get asked the question すしを食べましたか。 (did you eat sushi?). You could reply by using は, and say something like すしは食べませんでした。

  • 1
    It's not necessarily unnatural either to reply with すしは食べた to "what did you eat", for one example, when you sense that the questioner wanted to save some food, whether it happens to be susi or not. – user4092 Sep 5 '18 at 4:34
  • Do you have another example? Because even in that situation I would feel that a simple sentence like すしは食べた。 without any 相槌 or something is quite unnatural – Breton Loïc Sep 5 '18 at 13:43
  • When the doctor asks the patient about a cause of food poisoning and the patient starts with what s/he has just remembered. If it's を in this case, it feels "sushi, period". However, it's correct to choose を for "what you did" in general. – user4092 Sep 5 '18 at 21:14
  • Either of my examples is not strongly contrastive. However, you use は like this when it implies possible reference to another topic. – user4092 Sep 5 '18 at 21:34

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