は vs が — topic and subject

2026-10-16

は (wa) and が (ga) trip up almost every learner, and Mongolian speakers are no exception. Translating both as one “subject marker” will confuse you. Think of it this way.

The core idea

• は sets the topic, what you are talking about. It means roughly “as for…”.
• が points directly at the subject of an action or state. It is used for new information, answers to questions and emphasis.

Mongolian has no exact equivalent particle. The subject normally has no ending at all; topics are marked through «бол», the «нь» suffix, word order and stress.

Known versus new information

私は学生です。

As for me, I am a student. “I” is the topic.

あそこに猫がいます。

There is a cat over there. The cat is new, so が.

Mention the cat again and it is now known, so は:

その猫は白いです。

That cat is white.

In Mongolian, «Тэнд муур байна. Тэр муур цагаан» uses the pointing word «тэр» to show the cat is already known. Japanese does this job with は/が.

Answering a question

誰が来ましたか。
田中さんが来ました。

Who came? The question word takes が, and the answer, which is the key information, takes が too. Compare:

田中さんは来ましたか。

Did Tanaka come? Tanaka is the topic, and we ask about the event.

Contrast

は often implies “but not the others”.

肉は食べますが、魚は食べません。

I eat meat, but I don’t eat fish.

Mongolian gets the same effect with «бол… харин…».

Quick rules

1. “A is B” is usually A は B です.
2. A question word as the subject takes が.
3. Contrast takes は.
4. Introducing something new takes が.
5. With 好き, 分かる, できる, いる, ある you will usually see が:

私は音楽が好きです。

I like music. Both appear: は for the topic (I), が for the thing liked (music).

Common mistakes

• Starting every sentence with 私は. Japanese drops the topic when it is clear.
• は after a question word: ✕ 誰は来ましたか → ○ 誰が来ましたか.

Practice: write five sentences about your family and explain to yourself why each uses は or が. See more in the grammar section, and read about に, で, を, へ.