Korean Casual Speech Deepened: -자, -니?, -구나, and 아/야

Korean casual speech runs on four moves: -자 is the casual “let’s” (영화 보자 — let’s watch a movie), -니? asks a friendly casual question (어디 가니? — where ya going?), -는구나/-구나 voices a realization (벌써 끝났구나 — oh, it’s already over!), and 아/야 calls someone by name (민수야!, 지은아!). You met 반말 (casual speech) in Level 1 as bare verb stems. Now we deepen it — and, just as importantly, learn the social ritual of agreeing to drop formalities.

You just finished telling travel stories in polite speech. But with close friends and 동갑 (same-age peers), Koreans don’t stay formal forever. At some point one person says 우리 말 놓자 (let’s speak casually), and the whole register shifts. This lesson gives you the four endings that make 반말 sound natural — plus the etiquette of when to use it.

Ten words for going casual

These come up exactly when two people decide to drop the formalities.

The four casual endings — -자, -니?, -구나

Three of the four moves attach straight to a verb or adjective stem. -자 turns a sentence into a casual suggestion (“let’s”), -니? turns it into a friendly casual question, and -는구나/-구나 voices a sudden realization or exclamation.

Note the small differences: -자 is the casual partner of polite 봐요/봅시다. -니? is softer and warmer than a bare 어디 가? — it often carries a caring or gentle tone. For -구나, verbs take -는구나 (먹는구나) while adjectives and 이다 take plain -구나 (예쁘구나, 학생이구나); past tense always uses -구나 (끝났구나).

Calling a name — 아/야

To call out to someone in casual speech, add the vocative particle 아 or 야 to their name. The choice follows the name’s final sound — exactly the vowel/consonant logic behind 이/가 and 을/를.

So vowel-final names take 야 (민수야, 영희야) and consonant-final names take 아 (지은아, 동혁아). This particle is strictly for close, equal, or younger people — you would never tack 아/야 onto an elder’s or a boss’s name.

Agreeing to go casual

Watch two same-age people drop 존댓말 and try out 반말 on the spot:

All four moves in one exchange: 말 놓자 and 가자 use -자 (let’s), 어디 가니? uses -니? (casual question), 잘하는구나 uses -구나 (realization), and 민수야 / 지은아 show 아/야 in action. Notice how the speakers ask first (말 놓을까요?) before switching — that consent ritual is the real lesson.

FAQ

When is it actually okay to switch to 반말? 반말 (casual speech) is for people you’re close to and roughly equal or younger: close friends, 동갑 (same-age peers), younger siblings, or someone clearly junior who’s agreed to it. The crucial rule is that you don’t just drop into it — you ask or agree first: 우리 말 놓을까요? or 말 놓자 (let’s speak casually). Using 반말 with a stranger, someone clearly older, or in a formal setting sounds rude, so when in doubt, stay in 존댓말 (polite speech) until both sides agree to switch. Among 동갑 friends, switching to 반말 is a warm sign you’ve become close.

What’s the difference between -니? and just dropping the ending in a casual question? Both are casual, but they feel different. -니? (어디 가니? 밥 먹었니?) is a softer, warmer, slightly caring question ending — common from parents, older friends, or anyone being gentle. Simply dropping the ending with rising intonation (어디 가? 밥 먹었어?) is the most everyday casual question and sounds very natural among close friends. -니? can sound a touch old-fashioned or affectionate depending on who says it, while bare 어디 가? is neutral casual. Both are correct 반말 — pick -니? when you want a softer, kindlier tone.

How do I know whether to add 아 or 야 to someone’s name? Look at the last sound of the name. If it ends in a vowel, add 야: 민수 → 민수야, 영희 → 영희야. If it ends in a consonant (a 받침), add 아: 지은 → 지은아, 동혁 → 동혁아. This vocative particle is only for casual address among close, equal, or younger people — you’d never call an elder or boss with 아/야. Note this is the same vowel/consonant logic behind many Korean particles (이/가, 을/를): consonant-final words take the form with a vowel up front.

Next: direct quotation — reporting what others said. Previous: telling travel stories. Full path: curriculum hub.