We’ve seen the が particle used in certain grammatical expressions like:

先生が好きです = I like the teacher.

(先生 = せんせい/teacher. が = ga particle. 好きです = すきです/like)

and 傘がありません = I don’t have an umbrella.

(傘 = かさ/umbrella. が = ga particle. ありません = don’t have)

There are also other uses of が. The が particle can be used for emphasis:

山下さんがそれをします = Mr. Yamashita will do it (that).

(山下 = やました/Yamashita. さん = Mr. が = ga particle. それ = that/it. を = direct object particle. します = do)

Also, が is used after interrogative words:

誰が来ましたか = Who came [here]?

(誰 = だれ/who. が = ga particle. 来ました = きました/came. か = question marking particle.)

が is also used as a topic marking particle of a sentence:

あの人が鈴木さんです。彼女はここの学生です = That person over there is Ms. Suzuki. She is a student here.

(あの = That over there. 人 = ひと/person. が = ga particle. 鈴木 = すずき/Suzuki. さん = Ms. です = is.)

(彼女 = She. は = subject marking particle. ここ = here. の = possession marking particle. 学生 = student.です = is)

The first sentence uses が because the topic of the conversation concerning Ms. Suzuki hasn’t been introduced yet. The second sentence uses は because Ms. Suzuki has already been introduced and therefore she is now the subject of the sentence. Therefore が is used when we haven’t been introduced to someone’s identity yet.

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