What is the Subject Particle?
In Korean, particles are attached to nouns to show their grammatical function in a sentence. The particles 이/가 are subject particles .
They mark the noun they are attached to as the subject of the sentence—the person or thing that is doing an action or being described.
Key Functions:
Attaches directly to a noun.
Identifies the subject of the predicate (verb or adjective).
Answers the question "who?" or "what?" performed the action or has the quality.
For example, in the sentence 고양이가 자요 (The cat is sleeping), 가 tells us that the cat ( 고양이 ) is the one who is sleeping.
Choosing Between 이 and 가
The choice between 이 and 가 depends on whether the noun it attaches to ends in a consonant or a vowel. This is a very common rule in Korean grammar.
Rule Summary
Last Sound of Noun · Particle · Example
Consonant (받침) · 이 · 책 + 이 → 책이
Vowel (no 받침) · 가 · 의자 + 가 → 의자가
Examples with Consonants (받침 O)
사람 + 이 → 사람이 (person)
학생 + 이 → 학생이 (student)
음식 + 이 → 음식이 (food)
Examples with Vowels (받침 X)
친구 + 가 → 친구가 (friend)
나무 + 가 → 나무가 (tree)
아기 + 가 → 아기가 (baby)
이/가 in Different Sentence Types
The subject particle 이/가 is used in all basic types of Korean sentences.
1. With Action Verbs
The subject is the "doer" of the action.
아기가 울어요.
친구가 와요.
바람이 불어요.
2. With Descriptive Verbs (Adjectives)
The subject is what is being described.
날씨가 좋아요.