Information Structure in Korean: Focus, Topic, and Omission

Core examples: 저는 학생이에요; 제가 할게요; 그건 알아요; 먹었어요?; 누가 왔어요?; 커피는 마셨고 밥은 안 먹었어요.

Korean often says less because context says more

English-speaking learners often feel that Korean sentences are missing subjects, objects, or pronouns. 먹었어요? can mean “Did you eat?” without saying you. 제가 할게요 means “I will do it” with focus on me. 그건 알아요 means “As for that, I know.” Korean does not omit randomly. It omits what the listener can recover and marks what needs discourse attention.

Information structure is the grammar of what is already known, what is new, what is contrasted, and what can remain unsaid.

Topic: what the sentence is about

은/는 often marks topic or contrast. 저는 학생이에요 introduces or frames information about me. 그건 알아요 marks “that” as the thing under discussion. 커피는 마셨고 밥은 안 먹었어요 contrasts coffee and rice/meal.

Topic is not the same as subject. In 저는 학생이에요, 저 is both the topic and semantically the person being described. In 이 책은 제가 읽었어요, 이 책은 is the topic, while 제가 is the subject of reading. English “subject” cannot explain the Korean sentence alone.

Focus: what answers the current question

이/가 often marks the subject, but it can also carry focus or new information. 누가 왔어요? asks for the focused subject. 제가 할게요 answers “I will do it,” often with focus on the speaker taking responsibility.

Compare:

These are tendencies, not mechanical translations.

Omission: recoverable arguments disappear

Korean commonly omits subjects and objects when context makes them clear:

먹었어요? 네, 먹었어요.

The subject and object can be omitted because the situation supplies them. Adding 저는 그것을 먹었어요 may sound overexplicit unless contrast or clarification is needed.

Omission is common in conversation, messaging, service interactions, and narratives. It also appears in formal writing when repeated subjects would be redundant.

Contrast creates explicit marking

Korean often makes contrast explicit with 은/는:

커피는 마셨고 밥은 안 먹었어요.

The sentence does not merely report two facts. It contrasts categories. This is why 은/는 is common when correcting assumptions: 저는 괜찮은데 친구가 힘들어해요.

News and narratives manage topic continuity

A news article may introduce an entity with a full noun phrase, then omit or replace it once the topic is established. A narrative may introduce a character, then continue with omitted subjects until a new actor appears. Readers track topic continuity rather than expecting every sentence to restate pronouns.

This is one reason machine translation can make Korean sound pronoun-heavy in English or English sound overexplicit in Korean.

Technical-review guardrail: omission is grammatical, not sloppy

The article treats omitted subjects and objects as discourse-managed recoverability, not incomplete grammar. It also keeps 은/는 and 이/가 from being reduced to “topic vs subject” only; focus, contrast, givenness, and grammatical role all interact.

Remediation upgrade: omission is recoverability, not deletion practice

The v2 pass clarifies that omitted subjects and objects are recoverable from discourse, not simply optional words learners may drop anywhere. When several possible actors are active, Korean restores names, titles, particles, or pronouns. In translation, English may require recovered pronouns, but Korean production should not reinsert them unless contrast or clarity demands it.

Mini practice: mark the information structure

Learner workflow: information-structure routine

1. Ask what is already known in the conversation.
2. Mark what is new or focused.
3. Identify contrastive topics with 은/는.
4. Identify focused or new subjects with 이/가.
5. Recover omitted arguments from the immediate context.
6. When producing Korean, omit pronouns that are obvious unless contrast or clarity requires them.

Suggested functions:

1. Dialogue input: user enters short Korean exchange.
2. Topic labels: marks 은/는 phrases.
3. Focus labels: marks 이/가 answers and wh-question targets.
4. Omission resolver: lets users infer missing subjects/objects.
5. Pronoun-reduction exercise: converts overexplicit learner Korean into natural Korean.

Final rule

Korean does not leave words out because it is vague. It leaves recoverable material unsaid and marks the information that matters now.