이/가 for New Information & Wh-Answers

The subject particle 이/가 does more than say "this is the subject." In its sharpest use it carries focus: it presents its noun as new, freshly identified, or exhaustively selected — the "it is THIS one" reading. This is the exact opposite of what topic 은/는 does, and it explains a cluster of rules that otherwise look arbitrary: why "who called?" and its answer both take 가, why "there's a problem" takes 가, and why answering with 은/는 makes a native speaker feel you dodged the question. If 은/는 is the particle of known, 이/가 is the particle of news.

Wh-questions and their answers demand 이/가

A question like "who came?" is a request to fill an unknown slot — the who is precisely the new information being sought. So the question word takes 이/가, and the answer, which supplies that new information, takes 이/가 right back. Using 은/는 anywhere here is wrong, because there's nothing "known" to frame as a topic.

Read the answers carefully: 민수가 전화했어요 doesn't merely report that Minsu called — it says Minsu, specifically, is the one who called, singling him out from everyone who didn't. That exhaustive "it's Minsu (and no one else)" flavor is the focus meaning of 가. Swap in 민수는 and you've said "as for Minsu, he called," which sounds like you've quietly changed the subject to Minsu rather than answering who.

Presentational sentences: brand-new on the scene

The same focus logic drives "there is / here comes / suddenly there was" sentences. When a subject is being introduced for the first time — brought onto the scene — it's new by definition, so it takes 이/가. This is the natural home of the existence verbs 있다/없다 and of sudden-arrival verbs like 오다.

Each of these puts something new in front of the listener — a problem, the bus, snow, rain — none of which was under discussion a moment ago. That's why they can't take 은/는: there's no established topic to comment on, only a fresh fact to announce. 문제는 있어요 would flip the meaning to "a problem, I do have (but…)," a contrast, not a plain "there's a problem."

The English parallel: clefts and stress

English does have ways to mark this focus — it just doesn't use a particle. It reaches for a cleft ("it is Minsu who called") or heavy stress ("MINSU called"). Korean folds that exact emphasis into the single syllable 가.

Because the focus is inside the particle, Korean word order doesn't have to change and no extra "it is… who…" scaffolding is needed. This is elegant, but it also means the emphasis is easy for an English speaker to drop, since we're used to signalling it with intonation. Marking 제가 rather than 저는 when you volunteer to pay is the difference between "I'll get it" (stepping up) and "as for me, I'll pay" (oddly detached).

Exhaustive selection: "it's X, and only X"

Push the focus reading a little further and you get exhaustive identification: 가 can assert that its noun — and no other candidate — fits the predicate. This is why 제가 했어요 in answer to "who did this?" means "I did it (it was me)," accepting sole responsibility, where 저는 했어요 would merely say "as for me, I did (it)."

Introduced with 가, then continued with 는

The clearest way to feel 이/가's "new" meaning is to watch a referent enter a story and then settle in. The moment something appears, it's new — so it takes 가. From the next sentence on, it's shared knowledge — so it switches to 는. This is the same a → the handoff you saw on the topic-vs-subject page, viewed from the 이/가 side.

If you kept 가 on the second sentence (그 남자가 길을 물어봤어요), it would sound like you're re-introducing or re-focusing him — "it was that man who asked" — as if answering "who asked?" That's not wrong, it just shifts the meaning back toward focus. The particle tracks, sentence by sentence, whether the noun is news or old news.

The flip side of known-topic 은/는

Step back and the whole system is one axis. 은/는 sits at the known end: it frames information the listener already has. 이/가 sits at the new end: it introduces, identifies, and singles out. Every rule on this page is just that axis in action — wh-answers, "there is…," clefts, and exhaustive selection are all species of new/focused information, and new is 이/가's job. When you're unsure which to use, the decision tree walks the axis step by step; the full contrast is on 은/는 vs 이/가.

Common Mistakes

1. Answering a wh-question with 은/는. The reply to "who?" supplies the new, sought item — it must be 이/가.

2. Using 은/는 in a "there is / are" sentence. A newly-introduced existent takes 이/가; 은/는 turns it into a contrast.

3. Forgetting the contraction in the question word — ×누구가. 누구 + 가 contracts to 누가.

4. Introducing a brand-new subject with 는. Something arriving on the scene is new, so it takes 가; it only switches to 는 once it's established.

Key Takeaways

• 이/가 carries focus: it presents its noun as new, identified, or exhaustively selected — "it is THIS one."
• Wh-questions and their answers demand 이/가 (누가 전화했어요? — 민수가 전화했어요), never 은/는.
• "There is / here comes" presentational sentences take 이/가 (문제가 있어요, 눈이 와요); 은/는 would flip them to contrast.
• English marks this focus with a cleft or stress ("it's Minsu who…"); Korean packs it into the particle 가, so don't lose it by defaulting to 저는.
• This is the exact flip side of known-topic 은/는 — same axis, opposite end. See 은/는 vs 이/가 and the decision tree.