Subject Marker (이/가)
이/가
이/가 marks the grammatical subject of a sentence, identifying who or what performs an action or exists.
Pattern
Noun + 이 (after consonant) / 가 (after vowel)
Explanation
이 and 가 are subject-marking particles. Use 이 after a noun ending in a consonant and 가 after a noun ending in a vowel. They identify the doer of an action or the thing that exists or has a quality.
이/가 is used when introducing new information, answering 'who' or 'what' questions, or with certain predicates like 있다/없다 (to exist/not exist), 좋다 (to be good), and 필요하다 (to be needed). For example, '날씨가 좋아요' (The weather is nice) uses 가 to mark the subject 날씨.
The difference between 이/가 and 은/는 is one of the trickiest aspects of Korean. Generally, 이/가 introduces new information or focuses on the subject, while 은/는 marks known information or the topic. In '누가 왔어요?' (Who came?), 가 marks the unknown subject. In the answer '민수가 왔어요' (Minsu came), 가 identifies the specific person.
Examples
날씨가 좋아요.
Nalssi-ga joayo.
The weather is nice.
물이 필요해요.
Mul-i piryohaeyo.
Water is needed.
누가 왔어요?
Nuga wasseoyo?
Who came?
시간이 없어요.
Sigan-i eopseoyo.
There is no time.
비가 와요.
Bi-ga wayo.
It is raining.
Common Mistakes
Wrong
날씨이 좋아요.
Correct
날씨가 좋아요.
날씨 ends in a vowel, so use 가, not 이.
Wrong
물가 필요해요.
Correct
물이 필요해요.
물 ends in a consonant (ㄹ), so use 이, not 가.
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