-이 is the subject marker used when a noun ends in a consonant.
It indicates who or what is performing an action.
It helps emphasize the subject of the sentence.
-이 is used with consonant-ending nouns (e.g., 사람이, 책이).
-가 is used with vowel-ending nouns (e.g., 고양이가, 학교가).
The suffix -이 is a subject marker that is attached to nouns ending in a consonant to indicate that they are the subject of a sentence. It works in the same way as -가, which is used for nouns ending in a vowel.
Usage of -이: NC-이
Marking the Subject of a Sentence
-이 is attached to nouns that end in a consonant to show that they are performing the action or being described.
If a noun ends in a vowel, -가 is used instead.
Examples:
학교 (“school”) → 학교가 크다. (“The school is big.”) → Ends in a vowel, so -가 is used.
사람 (“person”) → 사람이 왔다. (“The person came.”) → Ends in a consonant, so -이 is used.
Emphasizing the Subject
-이 helps clarify who or what is performing an action, especially when making a distinction.
Example:
책이 떨어졌다. → “The book fell.” (Emphasizes that the book fell, not something else.)
고양이가 뛰어다닌다. → “The cat is running around.”
Comparison with Topic Markers (-은 / -는)
While -이 (or -가) specifically marks the subject, the topic markers -은 / -는 are used for contrast or general statements.
Example:
한국어는 어렵다. → “Korean (in general) is difficult.”
한국어가 어렵다. → “Korean is difficult.” (Focusing on Korean itself, rather than a comparison.)
See also
-가, -은, -는