Disclaimer: I got this info from the lingodeer website. 🚩this is a very complicated concept in Korean and you will not learn in in one sitting. It comes to you with lots and lots of exposure and practice. I'm still not the best at it myself after studying for years, but I've noticed that I can just feel when it seems good or weird to use one over the other. After lots of exposure to the language you start to naturally know when It's best to use which one. So don't stress too much about this difference and let yourself make all the mistakes you need to. You'll start to pick up on it, I promise. Because of that, don't expect this post to be able to explain everything for you at once. You'll probably still be confused and that's okay. [original post]
Subject marking particles 이/가
To sum it up, 이 and 가 are used to denote the subject of a sentence.
• 이 is used after a noun that ends in a consonant. (E.g. 선생님이 / 책이 / 이름이 )
• 가 is used after a noun that ends in a vowel. (E.g. 학교가 / 엄마가 / 의자가 )
Let’s look at some example sentences:
신발이 더러워요. The shoes are dirty.
날씨가 추워요. The weather is cold.
민지가 학교에 갔다. Minji went to school.
강아지가 잠을 잡니다. The dog is sleeping.
비행기가 공항에 도착했습니다. The plane has arrived at the airport.
Topic marking particles 은/는
은 and 는 are used to denote the topic of a sentence.
• 은 is used after a noun that ends in a consonant. (E.g. 선생님은 / 책은 / 이름은 )
• 는 is used after a noun that ends in a vowel. (E.g. 학교는 / 엄마는 / 의자는 )
Here are some examples:
오늘은 날씨가 좋아요. The weather is nice today.
오늘 = “today”. It is the topic of the sentence.
그는 곧 결혼을 할 거예요. He’ll get married soon.
그 = “he”. It is the topic of the sentence.
Four Differences Between
은/는 and 이/가
Difference #1: Subject vs Description
이/가 puts the focus on the subject:
누가 이 컵을 깼어요? Who broke this cup?
가 puts the focus on “who” broke the cup.
제가 깼어요. I did.
가 puts the focus on the subject “I”, who broke the cup.
은/는 puts the focus on the description:
수진 씨는 지금 뭐 해요? What is Sujin doing now?
는 puts the focus on what Sujin is “doing”.
수진 씨는 지금 요리하고 있어요. Sujin is cooking now.
는 puts the focus on Sujin’s action, which is “cooking”.
Difference #2: New Information vs. Known Information
이/가 is used to introduce new information:
새로운 친구가 생겼어요. 그 친구는 17살이에요. I have a new friend. The friend is 17 years old.
Explanation: In the second sentence, the “friend” is no longer new information, because the friend was previously mentioned in the first sentence. That’s why you have to use “친구는”, and not “친구가” in the second sentence.
은/는 is used to mention known information:
어제 한국어 시험이 있었어요. 그 시험은 너무 어려웠어요. I had a Korean language test yesterday. That test was very difficult.
Explanation: Because the “test” is no longer new information, as it was previously mentioned in the first sentence, you have to use “시험은”, and not “시험이” in the second sentence.
Difference #3: Statements vs. Comparisons
이/가 is used to making broad statements:
드레스가 예뻐요. The dress is pretty.
시장에 사람이 많았어요. There were many people in the market.
은/는 is used in comparisons and contrasting:
저는 그림은 잘 그리지만 공부는 못해요. I’m good at painting, but I’m not good at studying.
철수는 키가 크고 지민이는 키가 작아요.
Cheolsu is tall and Jimin is short.
그 식당은 햄버거는 맛있어요. That restaurant has good hamburgers.
(This has the nuanced implication “but not the salad” or “but not their service” etc. , compared to their hamburger.)
Difference #4: Only after subject vs. After any noun
이/가 can be used only after the subject of a sentence:
케이크가 맛있어요. The cake is delicious.
고향이 어디십니까? Where is your hometown?
부산이 제 고향이에요. Busan is my hometown.
은/는 is used after any noun that requires emphasis:
저는 김지민입니다. I’m Jimin Kim.
이것은 책이에요. This is a book.
그것은 의자입니다. That is a chair.
Conclusions: 이/가 vs 은/는
Please note that these are some of the most complicated grammar rules in Korean. Even advanced Korean learners often get confused when trying to distinguish the correct use of 은/는 and 이/가.
The best way to better understand these particles is to read Korean texts as much as you can, while keeping the aforementioned explanations in mind.
If you have been learning about particles for awhile and want a way to practice & test yourself I recently made a quiz booklet for the most common Korean particles.