The subject marker 이/가 (i/ga) identifies the grammatical subject—who or what performs the action or is in a particular state. It's essential for indicating the actor in a sentence.
Form
- 이 (i) - after consonants
- 가 (ga) - after vowels
Basic Function
Marks the grammatical subject that performs the action or exists in a state.
Translation: Usually just the subject in English, with emphasis on "who/what."
Usage Examples
Identifying Who/What
When specifying who or what is doing something:
- 비가 와요. (Bi-ga wayo.) - Rain comes. / It's raining.
- 학생이 공부해요. (Haksaeng-i gongbuhaeyo.) - The student studies.
- 고양이가 자요. (Goyangi-ga jayo.) - The cat sleeps.
- 친구가 왔어요. (Chingu-ga wasseoyo.) - My friend came.
With Adjectives (States)
Describing states or qualities:
- 날씨가 좋아요. (Nalssi-ga joayo.) - The weather is good.
- 꽃이 예뻐요. (Kkochi yeppeoyo.) - The flower is pretty.
- 방이 커요. (Bang-i keoyo.) - The room is big.
- 음식이 맛있어요. (Eumsik-i masisseoyo.) - The food is delicious.
New Information
Introducing new information or answering "who" or "what" questions:
Q: 누가 왔어요? (Who came?) A: 친구가 왔어요. (My friend came.)
Q: 뭐가 있어요? (What's there?) A: 책이 있어요. (There's a book.)
When to Use 이/가
1. Answering Questions
When responding to "who" or "what" questions:
Q: 누가 했어요? (Who did it?) A: 제가 했어요. (I did it.)
Q: 무엇이 필요해요? (What's needed?) A: 펜이 필요해요. (A pen is needed.)
2. Neutral Descriptions
Making objective observations without contrast:
- 비가 와요. (It's raining.)
- 꽃이 피었어요. (Flowers bloomed.)
- 별이 빛나요. (Stars are shining.)
3. Emphasis on Subject
When emphasizing who specifically did something:
- 제가 만들었어요. (It was ME who made it. / I'm the one who made it.)
- 동생이 깼어요. (It was my sibling who broke it.)
4. Existential Sentences
With 있다/없다 (to exist/not exist):
- 시간이 있어요. (There's time. / I have time.)
- 책이 있어요. (There's a book. / A book exists.)
- 돈이 없어요. (There's no money. / I don't have money.)
- 친구가 없어요. (There are no friends. / I have no friends.)
5. Natural Phenomena
Events that happen without a conscious agent:
- 비가 와요. (It rains.)
- 눈이 와요. (It snows.)
- 해가 떠요. (The sun rises.)
- 바람이 불어요. (Wind blows.)
Common Patterns
Pattern 1: Subject + Action Verb
[Noun + 이/가] + [Verb]
- 학생이 공부해요. (Student studies.)
- 고양이가 뛰어요. (Cat runs.)
- 친구가 와요. (Friend comes.)
Pattern 2: Subject + Adjective
[Noun + 이/가] + [Adjective]
- 날씨가 좋아요. (Weather is good.)
- 집이 커요. (House is big.)
- 물이 차가워요. (Water is cold.)
Pattern 3: Subject + Existence
[Noun + 이/가] + [있다/없다]
- 시간이 있어요. (There's time.)
- 돈이 없어요. (There's no money.)
- 사람이 많이 있어요. (There are many people.)
Pattern 4: Question Word + 이/가
[Question word + 이/가] + [Verb]
- 누가 왔어요? (Who came?)
- 뭐가 필요해요? (What's needed?)
- 어디가 아파요? (Where hurts?)
With Double Subjects
Korean allows topic + subject in one sentence:
[Topic + 은/는] + [Subject + 이/가] + [Predicate]
- 저는 시간이 없어요. (As for me, time doesn't exist. / I don't have time.)
- 친구는 키가 커요. (As for my friend, height is tall. / My friend is tall.)
- 한국은 음식이 맛있어요. (As for Korea, food is delicious. / Korea has delicious food.)
This construction describes a characteristic or possession of the topic.
Subject Emphasis
Using 이/가 instead of 은/는 emphasizes the subject:
With 이/가 (Emphasis):
- 제가 했어요. (It was ME who did it.)
- 누나가 만들었어요. (It was my SISTER who made it.)
With 은/는 (Topic):
- 저는 했어요. (As for me, I did it.)
- 누나는 만들었어요. (As for my sister, she made it.)
Subject vs Object
Don't confuse 이/가 (subject) with 을/를 (object):
Subject (이/가): Who/what performs action
- 학생이 책을 읽어요. (Student reads book.)
- 고양이가 쥐를 잡아요. (Cat catches mouse.)
Object (을/를): What receives action
- 학생이 책을 읽어요. (Student reads book.)
- 고양이가 쥐를 잡아요. (Cat catches mouse.)
With Transitive vs Intransitive Verbs
Intransitive Verbs (No object)
Only need a subject:
- 아기가 자요. (Baby sleeps.)
- 학생이 와요. (Student comes.)
- 꽃이 피었어요. (Flower bloomed.)
Transitive Verbs (Take object)
Need both subject and object:
- 학생이 (subject) 책을 (object) 읽어요. (Student reads book.)
- 고양이가 (subject) 물을 (object) 마셔요. (Cat drinks water.)
Subject Omission
When the subject is obvious from context, it's often omitted:
With subject:
- 비가 와요. (It rains.)
Subject omitted (context clear):
- 와요. (Rains/comes.)
Question-answer context: Q: 누가 했어요? (Who did it?) A: 제가 했어요. (I did it.) - Subject kept for clarity
Q: 뭐 해요? (What are you doing?) A: (저는) 공부해요. (Studying.) - Subject often omitted
Comparing 이/가 and 은/는
이/가 marks the grammatical subject:
- New information
- Neutral observation
- Answering "who/what"
- Emphasis on the subject
은/는 marks the topic:
- Known information
- Establishing context
- Contrast (implicit or explicit)
- General statements
See "은/는 vs 이/가 Explained" for detailed comparison.
Special Cases
With Question Words
Always use 이/가 with interrogatives:
- 누가 왔어요? (Who came?) - Always 가, never 는
- 뭐가 있어요? (What's there?) - Always 가, never 는
- 어디가 아파요? (Where hurts?) - Always 가, never 는
With Negative Existentials
- 시간이 없어요. (There's no time.)
- 돈이 없어요. (There's no money.)
- 친구가 없어요. (There are no friends.)
Using 이/가 keeps it neutral; using 은/는 would add contrast.
Common Expressions with 이/가
제가 (jega) - I (subject, polite)
- Used when emphasizing you're the one doing something
누가 (nuga) - who (subject)
- 누가 왔어요? (Who came?)
뭐가/무엇이 (mwoga/mueosi) - what (subject)
- 뭐가 필요해요? (What's needed?)
이게/이것이 (ige/igeosi) - this (subject) 그게/그것이 (geuge/geugeosi) - that (subject)
In Relative Clauses
When modifying nouns, the subject within the clause uses 이/가:
- 친구가 읽는 책 (The book that friend reads)
- 비가 오는 날 (Days when rain falls)
- 제가 좋아하는 음식 (Food that I like)
Key Points
- ✅ Form: 이 after consonants, 가 after vowels
- ✅ Function: Marks the grammatical subject
- ✅ Usage: New info, answering who/what, neutral observations, emphasis
- ✅ With adjectives: Describes who/what has a quality
- ✅ With 있다/없다: Marks what exists or doesn't exist
- ✅ Question words: Always use 이/가 with 누가, 뭐가, etc.
Understanding 이/가 is crucial for proper Korean sentence structure. It clearly identifies who or what is performing actions or existing in states.