Subject Particles 이/가 in Korean

Overview

The subject particles 이 and 가 are among the first grammar particles learned at the CEFR A1 level. They mark the grammatical subject of a sentence — the person or thing performing the action or being described. The choice between 이 and 가 depends purely on phonetics: 이 follows consonant-ending nouns, while 가 follows vowel-ending nouns.

These particles are distinct from the topic particles 은/는, and understanding the difference between subject and topic marking is one of the most nuanced aspects of Korean grammar. At the A1 level, the key point is that 이/가 introduces new information, identifies a specific subject, or answers "who/what" questions.

Mastering subject particles is essential because they appear in virtually every Korean sentence and interact with other grammatical patterns throughout all proficiency levels.

How It Works

Noun ending	Particle	Example
Consonant	이	물이 (water + subject)
Vowel	가	날씨가 (weather + subject)

Key uses of 이/가:

1. New information: Introducing something not yet mentioned
2. Identification: Answering who or what questions
3. Existence/description: With 있다/없다 and descriptive verbs
4. Emphasis: Highlighting specifically who or what

Use	Example	Translation
New info	비가 와요.	It's raining. (rain is coming)
Identification	누가 했어요? — 제가 했어요.	Who did it? — I did.
Existence	시간이 없어요.	There's no time.
Description	꽃이 예뻐요.	The flower is pretty.

Examples in Context

Korean	Romanization	English	Note
날씨가 좋아요.	nal-ssi-ga jo-a-yo	The weather is good.	vowel ending → 가
물이 필요해요.	mu-ri pi-ryo-hae-yo	Water is needed.	consonant ending → 이
누가 왔어요?	nu-ga wa-sseo-yo	Who came?	question word + 가
제가 할게요.	je-ga hal-ge-yo	I will do it.	emphasis on "I"
비가 와요.	bi-ga wa-yo	It's raining.	new information
고양이가 있어요.	go-yang-i-ga i-sseo-yo	There is a cat.	existence
문제가 뭐예요?	mun-je-ga mwo-ye-yo	What is the problem?	identification
머리가 아파요.	meo-ri-ga a-pa-yo	My head hurts.	body part as subject
전화가 왔어요.	jeon-hwa-ga wa-sseo-yo	A call came.	new event
맛이 어때요?	ma-si eo-ttae-yo	How is the taste?	consonant ending → 이

Common Mistakes

Confusing 이/가 with 은/는

• Wrong: Using 은/는 when answering "who" questions: 누가 했어요? — 저는 했어요.
• Right: 누가 했어요? — 제가 했어요.
• Why: 이/가 identifies new information; 은/는 marks the topic (already known information). "Who" questions demand 이/가 in the answer.

Using the wrong particle based on final sound

• Wrong: 날씨이 좋아요.
• Right: 날씨가 좋아요.
• Why: 날씨 ends in a vowel (ㅣ), so it takes 가. This is a phonetic rule with no exceptions.

Overusing 이/가 where topic particle is more natural

• Wrong: 저가 한국 사람이에요. (stating general fact about yourself)
• Right: 저는 한국 사람이에요.
• Why: When making general statements about yourself as a topic of conversation, 은/는 is more natural.

Usage Notes

In casual speech, 이/가 is sometimes dropped, especially when the subject is obvious. However, dropping it can change the nuance. In formal and written Korean, subject particles are consistently used. The special humble form 제가 (from 저 + 가) is very common in polite speech when emphasizing "I" as the doer.

Practice Tips

• After each "who/what" question, practice answering with 이/가 to build the habit of marking new information correctly.
• Create pairs of sentences using both 이/가 and 은/는 with the same noun to feel the difference in nuance.
• When reading Korean, circle every 이/가 you find and identify why the subject particle was chosen over the topic particle.

Related Concepts

• Prerequisite: Basic Sentence Structure — understanding SOV order is needed before learning particles
• Next steps: Topic Particle 은/는 — learn the topic marker and how it contrasts with 이/가