Eun/Neun vs I/Ga (은/는 vs 이/가): Which One Do I Use?

Ask what the predicate is before you choose between them. An adjective cannot take an object, so the noun it goes with cannot take 을/를: it takes 이/가, or 은/는 when you are contrasting. A verb takes 을/를. Only once the slot is settled do the four 은/는 versus 이/가 rules come into it.

A typical explanation skips that step and starts with the four rules, which is why this particle feels unlearnable. You are being asked to choose between two options in a slot that has not been decided yet.

Floor one: what kind of word is the predicate

Two Korean sentences that translate the same into English take different particles, because one uses an adjective and the other a verb.

Both are correct and they mean nearly the same thing. What changed is the part of speech, not the meaning, and the particle follows the part of speech.

Korean adjectives behave like verbs and sit at the end of a sentence, so 좋다, 아프다, 필요하다, 있다, 없다 and 많다 all work this way. English calls them adjectives and then does nothing else with the fact. Korean uses it to decide the slot.

⚠️ Rule 0 decides the slot, not the final particle. An adjective blocks 을/를 only. 은/는 can still sit on top of that slot: 저는 시간은 없어요 is fine when you are contrasting.

Floor two: the four rules

Now that the slot is settled, this is the whole set. Two for 은/는, two for 이/가.

1. 은/는, default. Talking about yourself, or making a general statement.
2. 은/는, contrast. Two things held against each other.
3. 이/가, answering "who?" The slot that answers the question gets 이/가.
4. 이/가, new information. Something appearing, or being introduced for the first time.

Rules 3 and 4 are the same idea from two directions. 이/가 points at the slot that carries the news, whether the news is an answer or something that just appeared.

The one that catches everyone

Rule 3 is the reason 저는 and 제가 are not interchangeable. 저는 학생이에요 is you telling somebody about yourself. 제가 학생이에요 is you being the answer to a question about who.

Said in the wrong place, the second one sounds like you are correcting somebody nobody was arguing with. This one tends to get noticed where most particle slips do not.

What to stop doing

• Stop translating "is". English has one verb where Korean has adjectives, 이다 and 있다, and the noun in front of each behaves differently. The English sentence cannot tell you which.
• Stop looking for a topic marker rule. Calling 은/는 a topic marker describes its job accurately. What it does not do is help you choose while a sentence is already coming out of your mouth.
• Stop treating this as one decision. It is two, and the first one is usually easy once you know to ask it.

What to do this week

1. Take ten sentences you already say and mark the predicate as adjective or verb. That is floor one and it is quick.
2. For each adjective sentence, check that the thing before it has 이/가 rather than 을/를.
3. Say 저는 학생이에요 and 제가 학생이에요 out loud and say aloud what each is answering.
4. Leave the exceptions alone for now. Getting floor one automatic removes most of the errors you are making.

The short version

The verb picks the slot first. Then 은/는 for default and contrast, 이/가 for answers and new information. Learning them in that order is the whole difference, and it is why the four rules on their own never stuck.

Read next

• Textbook Korean vs Real Korean: How Do I Stop Sounding Like a Book?
• Why Can I Understand Korean but Not Speak It?