The particle が

N が N ga Marks the subject; this one, not another

が (ga) marks the subject, often the new or important part. 誰が来ましたか: who came? English does this with stress and short answers.

Level: JLPT N5, beginner
Type: Particles
English links: subjects, short answers, emphasis, verbs of liking

What it means

が marks the subject of the sentence: the person or thing that does the action, or has the quality. In 田中さんが来ました, Tanaka-san is the one who came.

So how is it different from は? Here is the simple version I give colleagues. は says "here is what we are talking about", and the weight falls on what comes after it. が says "this one, and not another", and the weight falls on the noun before it. Ask 誰が来ましたか (Who came?) and the answer is 田中さんが来ました, because Tanaka-san is the new information.

Two quick rules help. A question word never takes は: say 誰が, 何が, どれが. And the answer to a が question keeps が. Also use が for things you notice or report as news: 雨が降っています (It is raining), バスが来ました (The bus is here).

Some words always mark their thing with が, not を. The common ones at N5 are 好き (like), 上手 (good at), わかる (understand), ほしい (want), and ある and いる (there is). 私は猫が好きです is "I like cats". The person takes は, and the cats take が.

How to build it

Pattern	How it works
Noun + が + verb noun + ga + verb	Marks who or what does the action, often as new information.
Question word + が question word + ga	誰が, 何が, どれが. A question word cannot take は. The answer keeps が.
Noun + が + 好き / 上手 / わかる / ある / いる noun + ga + suki / jouzu / wakaru / aru / iru	These words mark their thing with が. English makes it the object: "I like cats".
A は B が + adjective a wa b ga + adjective	The whole takes は, the part takes が: 山田先生は英語が上手です.

Examples

誰が来ましたか。田中さんが来ました。 dare ga kimashita ka. tanaka-san ga kimashita. Who came? Tanaka-san did.
雨が降っています。 ame ga futte imasu. It is raining.
私は猫が好きです。 watashi wa neko ga suki desu. I like cats.
山田先生は英語が上手です。 yamada-sensei wa eigo ga jouzu desu. Yamada-sensei is good at English.
どれがいいですか。これがいいです。 dore ga ii desu ka. kore ga ii desu. Which one do you want? This one, please.

How English says it

English has no particle for the subject. It shows the subject by place: before the verb. "Tanaka-san came." The same sentence covers both は and が.

To say "this one, not another", English uses stress: "TANAKA-SAN came." It can also split the sentence to point at one part: "It was Tanaka-san who came." In speech, the short answer does the job: "Who came?" "Tanaka-san did."

The 好き / 上手 / わかる group is the other half of the story. Japanese puts the liked thing in the が slot. English makes it the object of a verb: "I like cats", "I understand English". The English subject is the person, who is often not said in the Japanese at all.

Why it can make English hard

好き works like an adjective in Japanese ("likeable"), with です after it. Many students treat "like" the same way and add "am": "I am like cats."
English shows new information with stress, not with a word. Students who read every word at the same strength lose the meaning that が carries.
Japanese answers a who question with the noun: 田中さんです or 田中さんが来ました. The English short answer, "Tanaka-san did", has no match in Japanese, so students may give the whole sentence or only the name.
With わかる and ある, Japanese often does not say the person. English needs "I understand" and "I have", so the subject can go missing: "Understand." "Have a pen."

Mistakes you will hear

I am like cats. I like cats. 好きです is "like" plus "is" in one. In English, "like" is the verb and needs no "am".
Yamada-sensei is good English. Yamada-sensei is good at English. 英語が上手 has no extra word. English needs "at" after "good".
Rain is falling. It is raining. 雨が降っています, word by word. Correct, but English usually says "It is raining".
Who came? Tanaka-san came. Who came? Tanaka-san did. Not wrong, but heavy. English answers with the subject and a short helping verb.

In the classroom

Play "Who did it?" Something happens in class: a pen falls, the door closes. Ask "Who dropped the pen?" Students answer with the short form and stress the name: "KENTA did."
Read pairs aloud: "I like CATS" (not dogs) and "I like cats" (no contrast). Let students hear that English stress does the job of が.
Make a two-column list. On the left, the Japanese が words: 好き, 上手, わかる, ほしい. On the right, the English verb and object: like, be good at, understand, want. Add to it through the year.

Practice

Try each one, then open it to check.

1. Fill the gap: 誰＿来ましたか。 (Who came?)

Answer: が

A question word takes が, never は.
2. Fill the gap: 私は犬＿好きです。 (I like dogs.)

Answer: が

好き marks the liked thing with が, not を.
3. Choose は or が. A: どれがいいですか。 B: これ＿いいです。

Answer: が

The question asks "which one" with が. The answer gives the new information, so it keeps が.
4. A student writes "I am like soccer." Fix it.

Answer: I like soccer.

"Like" is the verb. It needs no "am".
5. Translate: 雨が降っています。

Answer: It is raining.

English uses the verb "rain", with "it" as the subject.