Overview
The particle -이/가 is a fundamental subject marker in Korean grammar. It attaches directly to a noun or pronoun to clearly indicate that it is the grammatical subject of the sentence. This means the noun or pronoun marked with -이/가 is the one performing the action of the verb or being described by an adjective.
Usage
- Identifying the Performer/Entity: The primary role of -이/가 is to specify who or what is carrying out the action or is in a particular state. It answers the question "who/what is doing this?" or "who/what is like this?".
- Example: 책이 재미있어요. (The book is interesting.) - '책' (book) is the subject being described.
- Introducing New Information: -이/가 is frequently used when the subject is new to the conversation or when you are specifically identifying something for the first time. It brings the subject into focus as the new piece of information.
- Example: 누가 왔어요? 제 친구가 왔어요. (Who came? My friend came.) - '친구' (friend) is new information.
- With Descriptive Verbs and Adjectives: It is commonly used with verbs like 있다 (to exist/have), 없다 (to not exist/not have), 되다 (to become), 아니다 (to not be), and with most adjectives.
- Example: 돈이 없어요. (I don't have money.)
- Emphasis on the Subject: While -은/는 marks the topic, -이/가 can place emphasis directly on the subject itself, often in contrast to other potential subjects or when making a specific, definitive statement.
Conjugation Rules
The choice between -이 and -가 depends on the final sound of the preceding noun or pronoun:
- If the noun ends in a consonant, attach -이.
- Example: 책 (chaek) + 이 → 책이
- Example: 집 (jip) + 이 → 집이
- If the noun ends in a vowel, attach -가.
- Example: 사과 (sagwa) + 가 → 사과가
- Example: 친구 (chingu) + 가 → 친구가
Knowledge Plus
- Distinction from -은/는: This is one of the most challenging concepts for beginners. While both -이/가 and -은/는 can mark subjects, their nuances differ significantly.
- -이/가 marks the grammatical subject, often introducing new information, identifying something specifically, or emphasizing the subject itself. It answers "who/what is it?".
- -은/는 marks the topic of the sentence, which can be the subject but often refers to existing information, general statements, or draws a contrast. It answers "as for X...".
- Think of -이/가 as highlighting what the subject is, and -은/는 as highlighting what is being said about the topic.
- Common Usage in Questions: -이/가 is very common in questions asking "who?" (누가) or "what?" (무엇이/뭐가) because these questions seek to identify a specific subject.
- Pronoun Changes: Note that some pronouns change form when -가 is attached:
- 나 (I) + 가 → 내가
- 너 (you) + 가 → 네가
- 저 (I, humble) + 가 → 제가
- 누구 (who) + 가 → 누가