-군(요)/구나 - Oh!/I see! | Korean Grammar Documentation

-군(요) and -구나 are sentence endings expressing realization, discovery, or exclamation. They mean "Oh!," "I see!," or indicate that the speaker has just learned or realized something. -군(요) is more formal/polite, while -구나 is casual and intimate.

Structure

Verb/Adjective stem + -군(요)/-구나

Breakdown:

-군: Realization ending (formal/polite)
-요: Polite marker (optional with -군)
-구나: Realization ending (casual/intimate)

Meaning: Expresses new discovery or strong realization

Formation Rules

Formal/Polite: -군(요)

Direct attachment to stem:

예쁘다 → 예쁘군요 (Oh, it's pretty!)
맛있다 → 맛있군요 (Oh, it's delicious!)
좋다 → 좋군요 (Oh, it's good!)
크다 → 크군요 (Oh, it's big!)
가다 → 가는군요 (Oh, they're going!)

Casual: -구나

Direct attachment to stem:

예쁘다 → 예쁘구나 (Oh, it's pretty!)
맛있다 → 맛있구나 (Oh, it's delicious!)
좋다 → 좋구나 (Oh, it's good!)
크다 → 크구나 (Oh, it's big!)
가다 → 가는구나 (Oh, they're going!)

Core Meaning: Strong Realization

Discovering New Information

Just learned something:

그렇군요! (Oh, I see! / Is that so!)
그랬구나! (Oh, that's how it was!)
이렇게 하는 거군요 (Oh, so this is how you do it!)
정말이구나! (Oh, it's really true!)

Exclamation of Surprise

Stronger than -네(요):

정말 예쁘군요! (Oh, it's really pretty!)
대단하구나! (Oh, that's amazing!)
벌써 끝났군요! (Oh, it's already finished!)
생각보다 어렵구나! (Oh, it's harder than I thought!)

Politeness Levels

Formal/Polite: -군요

Polite conversation, formal settings:

그렇군요 (Oh, I see)
좋군요 (Oh, that's good)
재미있군요 (Oh, that's interesting)

Polite (Less Common): -군

Without 요, more literary/formal:

그렇군 (Oh, I see - written/formal)
좋군 (Oh, that's good - written/formal)

Note: -군 alone sounds formal/old-fashioned in speech

Casual/Intimate: -구나

With close friends, family, children:

그렇구나 (Oh, I see)
좋구나 (Oh, that's good)
재미있구나 (Oh, that's fun)

Tense Variations

Present Realization: -군(요)/-구나

Discovering current state:

맛있군요 (Oh, it's delicious!)
춥구나 (Oh, it's cold!)
예쁘군요 (Oh, it's pretty!)

Past Realization: -았/었군(요)/-았/었구나

Discovering past fact:

벌써 갔군요 (Oh, they already left!)
그랬구나 (Oh, that's how it was!)
이미 끝났군요 (Oh, it already finished!)
비가 왔었구나 (Oh, it had rained!)

With Progressive: -고 있군(요)/-고 있구나

Discovering ongoing action:

공부하고 있군요 (Oh, you're studying!)
자고 있구나 (Oh, they're sleeping!)
비가 오고 있군요 (Oh, it's raining!)

Common Usage Patterns

Realization Expressions

Understanding something new:

그렇군요 (Oh, I see / That's right!)
아, 그렇군요 (Ah, I see!)
그랬구나 (Oh, that's how it was!)
이해했어요. 그렇군요 (I understand. Oh, I see!)

Exclamations

Strong reactions:

대단하군요! (Oh, that's amazing!)
정말이구나! (Oh, it's really true!)
놀랍군요! (Oh, that's surprising!)
멋있구나! (Oh, that's cool!)

Compliments and Admiration

Appreciating something:

정말 예쁘군요 (Oh, it's really pretty!)
잘하는구나! (Oh, you're good at this!)
훌륭하군요 (Oh, that's excellent!)
똑똑하구나! (Oh, you're smart!)

Discoveries

Just noticing:

여기 있었군요! (Oh, it was here!)
벌써 왔구나! (Oh, you're already here!)
이미 끝났군요 (Oh, it's already finished!)
생각보다 크구나 (Oh, it's bigger than I thought!)

Common Expressions

Understanding and Agreement

그렇군요 (Oh, I see)
아, 그렇군요 (Ah, I see)
알겠군요 (Oh, I understand)
맞군요 (Oh, that's right)

Surprise Discoveries

벌써 그렇게 됐군요 (Oh, it's already like that!)
그랬구나 (Oh, that's how it was!)
정말이군요 (Oh, it's really true!)
의외군요 (Oh, that's unexpected!)

Compliments (Polite)

정말 잘하시는군요 (Oh, you're really good at this!)
훌륭하군요 (Oh, that's excellent!)
대단하십니다 → 대단하시군요 (Oh, you're amazing!)

Compliments (Casual)

잘하는구나! (Oh, you're good!)
예쁘구나! (Oh, it's pretty!)
똑똑하구나! (Oh, you're smart!)
멋있구나! (Oh, it's cool!)

Negative Forms

Negative Discovery

안 + Verb/Adj + -군(요)/-구나:

안 좋군요 (Oh, it's not good)
안 맛있구나 (Oh, it's not delicious)
안 예쁘군요 (Oh, it's not pretty)

Verb/Adj + -지 않군(요)/-지 않구나:

좋지 않군요 (Oh, it's not good)
맛없구나 (Oh, it's not tasty)

Comparing -군(요) and -구나

Formality Difference

-군(요): Polite/formal

Use with: strangers, elders, formal settings
그렇군요 (Oh, I see - polite)
좋군요 (Oh, that's good - polite)

-구나: Casual/intimate

Use with: close friends, family, children, younger people
그렇구나 (Oh, I see - casual)
좋구나 (Oh, that's good - casual)

Same Meaning, Different Contexts

Examples:

비가 오는군요 (Oh, it's raining - polite)
비가 오는구나 (Oh, it's raining - casual)
예쁘군요 (Oh, it's pretty - polite)
예쁘구나 (Oh, it's pretty - casual)

Comparing -군(요)/구나 vs -네(요)

Both express discovery, but different strength:

-군(요)/구나: Stronger realization, more exclamatory
- 그렇군요! (Oh, I see! - stronger)
- 예쁘구나! (Oh, it's pretty! - exclamation)
-네(요): Softer realization, more conversational
- 그렇네요 (Oh, I see - softer)
- 예쁘네요 (Oh, it's pretty - gentle)

Usage difference:

-군요: More formal, written, or when strongly struck by discovery
-네요: More common in everyday conversation, softer

With Adverbs

Emphasizing Discovery

정말/진짜 (really):

정말 좋군요! (Oh, it's really good!)
진짜 맛있구나! (Oh, it's really delicious!)

역시 (as expected):

역시 그렇군요 (Oh, it's as expected!)
역시 어렵구나 (Oh, it's difficult as expected!)

생각보다 (than expected):

생각보다 크군요 (Oh, it's bigger than I thought!)
생각보다 쉽구나 (Oh, it's easier than I thought!)

Special Usage: Talking to Oneself

Self-Directed Discovery (구나)

Realizing something while alone:

아, 그렇구나 (Ah, so that's how it is - to self)
이렇게 하는 거구나 (Oh, so this is how you do it - to self)
여기 있었구나! (Oh, it was here! - finding something)

Note: -구나 common for self-talk

Perspective and Usage

When to Use -군(요)

Use when:

Formal or polite contexts
Discovering something with strong realization
Writing or formal speech
Want to sound more emphatic than -네요

Nuance:

More formal and literary feel
Stronger sense of "aha!" moment
Less common in casual daily conversation than -네요

When to Use -구나