grammar - How to differentiate between 'a' and 'the'

How to differentiate between 'a' and 'the'.

私は魚を食べた

Does the above specify the exact fish that I ate or a general fish. Either ways how would you say ...

1. ate a fish



2. ate the fish.

Answer

Japanese will not distinguish nouns like English does. A and The are both English particles that do not exist in Japanese. If you are looking for a linear translation, you won't find it.

In both cases, I would translate it as:

私は魚を食べた。

If I were to talk about a specific fish, then I would add more information to let the listener know what fish I ate. For example:

冷蔵庫にある魚を食べた。
I ate the fish that was in the fridge.

その魚を食べた。
I ate that fish.

As you study more Japanese, you will realize that particles in English and Japanese rarely line up, as is the case with the two you are asking about in this question.