개연성 (gaeyeonseong)

개연성 (gaeyeonseong) generally means the possibility that a given thing could happen. Going by the dictionary definition alone, it sounds as stiff as a statistics or probability term — but the place this word actually flies around the hottest is not a lecture hall. It’s the group chat the moment a drama finale ends. When a character who clearly died in episode 3 walks in during the last episode as a twin sibling, viewers all type the same sentence as if they’d agreed on it beforehand: 개연성이 없다 (gaeyeonseongi eopda) — “there’s no plausibility.” If you’re learning Korean through K-dramas, 개연성 (gaeyeonseong) is the word you’re guaranteed to run into, whether in the subtitles or in the comments.

This word is a ruler for measuring “is this something that could plausibly happen?” Its look-alike 필연성 (pillyeonseong) means “it could not possibly have gone any other way”; 개연성 (gaeyeonseong) leans toward “well, it makes sense that it would go that way.” It points at the space in between — not 100 percent, not 0 percent, just believable. So there are two big things this word gets attached to. One is a story. When a character suddenly changes personality, or an event blows up with no foreshadowing whatsoever, people say the 개연성 (gaeyeonseong) has collapsed. The other is a claim or a guess. When the evidence isn’t solid but the circumstances add up, you say 개연성은 있다 (gaeyeonseongeun itda), “there is some plausibility to it.”

The temperature is close to neutral, and a little analytical. It’s a word for handing down a judgment rather than gushing or venting, so even between friends in casual speech, something critic-like lingers in it. And because 개연성 (gaeyeonseong) is a noun, it carries no politeness level of its own. Polite versus casual is decided by the predicate that follows — 개연성이 없어 (gaeyeonseongi eopseo) / 개연성이 없습니다 (gaeyeonseongi eopseumnida).

Checking with the National Institute of Korean Language dictionary

개연성 (noun) A likelihood in general of something happening. [en] probablity — A likelihood in general of something happening. [ja] がいぜんせい【蓋然性】 — 一般的にある事柄が起こる可能性。 [es] probabilidad — En términos generales, posibilidad de que algo específico pueda suceder. [zh] 盖然性，或然性 — 一般来说事情发生的可能性。 — National Institute of Korean Language, Basic Korean Dictionary (krdict.korean.go.kr)

A Portuguese definition isn’t carried in the dictionary, so we should note that the line below is our own rendering. (pt) probabilidade — possibilidade geral de algo acontecer.

Below are five of the dictionary’s real usage examples, copied as they are, each with a note on the kind of setting it belongs to.

개연성이 있다. 개연성이 없다. — National Institute of Korean Language, Basic Korean Dictionary (krdict.korean.go.kr)

개연성이 있다 (gaeyeonseongi itda), “there is plausibility,” and 개연성이 없다 (gaeyeonseongi eopda), “there is no plausibility,” are this word’s base forms and by far its most common pair. Eighty percent of all drama reviews are settled inside these two sentences. If things connect, 있다 (itda). If they don’t, 없다 (eopda).

개연성이 높다. 개연성이 크다. — National Institute of Korean Language, Basic Korean Dictionary (krdict.korean.go.kr)

개연성이 높다 (gaeyeonseongi nopda), “the plausibility is high,” and 개연성이 크다 (gaeyeonseongi keuda), “the plausibility is great,” are one notch more precise than 있다/없다. You use them about something not yet settled, to say “the odds of it going that way are considerable.” You’ll hear them often in news commentary and in meetings.

주장의 개연성. — National Institute of Korean Language, Basic Korean Dictionary (krdict.korean.go.kr)

주장의 개연성 (jujangui gaeyeonseong), “the plausibility of a claim,” is proof that this word lives outside dramas too. You use it like this when you’re weighing whether someone’s statement holds together, even if it hasn’t been proven.

처음부터 끝까지 개연성이 없어서 말도 안 되는 이야기였어. — National Institute of Korean Language, Basic Korean Dictionary (krdict.korean.go.kr)

처음부터 끝까지 개연성이 없어서 말도 안 되는 이야기였어 (cheoeumbuteo kkeutkkaji gaeyeonseongi eopseoseo maldo an doeneun iyagiyeosseo) — “It had no plausibility from start to finish, so it was a ridiculous story.” The dictionary example is already a perfect drama review. It even comes with the casual ending “-었어 (-eosseo)” attached, so you can lift it straight into a real conversation with a friend.

A real conversation

Setting: Sunday night, the finale of a 12-episode drama has just ended. On the living room couch, the closing credits are rolling.

Emily: 뭐야, 이게 끝이야? 3회에서 죽은 사람이 갑자기 살아 돌아와? What? That’s the ending? The guy who died in episode 3 just comes back alive?

Jun-kyung: 나도 지금 좀 멍해. 솔직히 이건 개연성이 없지. I’m a bit stunned too. Honestly, this one has no plausibility.

Emily: 앞에 복선이라도 하나 깔았으면 몰라. 그냥 쌍둥이래, 쌍둥이. If they’d planted even one hint earlier, fine. But no — turns out it’s a twin. A twin.

Jun-kyung: 야, 쌍둥이는 진짜 마지막 카드야. 작가님이 회차에 쫓겼나 봐. Hey, the twin card is the absolute last resort. The writer must’ve been squeezed on episodes.

Emily: 근데 8회까진 좋았잖아. 감정선은 개연성 있게 차곡차곡 쌓았는데. But it was good up to episode 8, right? The emotional arc was built up plausibly, step by step.

Jun-kyung: 그러니까 더 아깝지. 딱 거기서 끝냈어야 됐어. Exactly, that’s what makes it such a waste. They should’ve ended it right there.

Using it this way sounds off

✗ (A friend is explaining why they were late) 아, 그거 개연성 있네. (a, geugeo gaeyeonseong itne.) ✓ (A friend is explaining why they were late) 아, 그럴 만하네. (a, geureol manhane.) — “Ah, that makes sense.” → 개연성 (gaeyeonseong) is an evaluative word for weighing whether a story or an argument hangs together. Slap it onto a friend’s small everyday explanation and the conversation turns into a judging panel — you sound like you’re playing critic.

✗ (Listening to a friend who just went through a breakup) 네 얘기는 좀 개연성이 없다. (ne yaegineun jom gaeyeonseongi eopda.) ✓ (Listening to a friend who just went through a breakup) 좀 갑작스럽긴 했네. 많이 놀랐겠다. (jom gapjakseureopgin haenne. manhi nollatgetda.) — “That was pretty sudden. You must have been really shaken.” → Use this word about something a person actually lived through, and you’re essentially grading their life like a work of fiction. 개연성 (gaeyeonseong) is for made-up stories and unverified claims, not for a person’s experience.

Example sentences by situation

1. On a webtoon-based drama’s adaptation (with a friend, casual speech) This is where someone who read the original manhwa points out a scene the drama version dropped. If you also say what got cut and how that broke things, your review becomes far more convincing.

원작에선 이 장면 전에 편지가 한 통 오거든. 그걸 빼 버리니까 갑자기 개연성이 떨어져 (gaeyeonseongi tteoreojyeo). In the original, a letter arrives right before this scene. Once they cut that, the plausibility suddenly drops.

2. In a company meeting (polite speech) Outside of dramas, a formal review session like this is where 개연성 (gaeyeonseong) shows up most. It pairs well with a tone that leaves out emotion and offers only grounds.

이 시나리오는 개연성이 낮다고 (gaeyeonseongi natdago) 봅니다. 작년 데이터에 비슷한 사례가 한 건도 없었습니다. I’d say the plausibility of this scenario is low. There wasn’t a single comparable case in last year’s data.

3. Speculating while watching the news (casual speech) Use it when nothing is confirmed but the circumstances line up. It adds weight without declaring “this is a fact,” which makes it handy in careful conversations.

아직 확인된 건 아닌데, 개연성은 충분히 있어 보여 (gaeyeonseongeun chungbunhi isseo boyeo). Nothing’s confirmed yet, but it looks plenty plausible to me.

Politeness levels and similar expressions

개연성 (gaeyeonseong) is a noun, so it carries no honorific level by itself. The predicate that follows decides it — with a friend, 개연성이 없어 (gaeyeonseongi eopseo); in a meeting, 개연성이 없습니다 (gaeyeonseongi eopseumnida) or 개연성이 부족해 보입니다 (gaeyeonseongi bujokhae boimnida). Lining it up against similar words makes its seat at the table clearer.

Expression	Tone / intensity	Where it’s used
개연성 (gaeyeonseong)	Neutral, analytical	Drama takes, reviews, meetings. Works in both casual and polite speech
말이 되다 (mari doeda)	Colloquial, emotionally charged	Between friends. For worked-up moments like “이게 말이 돼? (ige mari dwae?)”
그럴듯하다 (geureoteuthada)	Neutral to slightly skeptical	Carries a “on the surface, sure” nuance. Can be praise or suspicion
설득력 (seoldeungnyeok)	Neutral, formal	Presentations, arguments. Focuses on the power to move the listener
핍진성 (pipjinseong)	Stiff, technical	Literary criticism, long-form reviews. Rarely used in everyday talk

About the very same scene, you’d tell a friend “야, 이게 말이 돼? (ya, ige mari dwae?)” but write in a review “후반부의 개연성이 아쉽다 (hubanbuui gaeyeonseongi aswipda),” “the plausibility in the back half is disappointing.” The meanings overlap, but they sit in different seats.

Cultural background — the viewers who audit plausibility

개연성 (gaeyeonseong) is a Sino-Korean word. It’s written 蓋然性: 蓋然 means “generally so,” and 性, meaning quality or nature, is attached to it. Literally, then, it’s “the quality of being generally so.” It started out as an academic term in logic and probability, and now it’s a word ordinary viewers use on a Sunday night.

There’s a reason for that migration. Korean dramas are often still being scripted while they air, and endings can wobble depending on ratings and viewer reactions. So it kept happening that a tightly woven early story got hastily folded up toward the end — and viewers needed an exact word to point at that collapse. 개연성 (gaeyeonseong) moved into that spot. The compound 개연성 붕괴 (gaeyeonseong bunggoe), “plausibility collapse,” has hardened into a fixed phrase, and in online communities people even fire it at writers as a blunt casual slogan: 개연성 챙겨라 (gaeyeonseong chaenggyeora), “get your plausibility together.” That usage isn’t in the dictionary, but on real internet boards it flies back and forth thousands of times a day.

The word gets used for praise, too. When a character doesn’t suddenly turn saintly, and the small scenes leading up to a breakup have been stacked up one by one, people say 개연성이 탄탄하다 (gaeyeonseongi tantanhada), “the plausibility is solid.” Which also means that what Korean viewers demand from a drama isn’t only shock and twists. The wish to be surprised and convinced — that demand is packed into this single word.

Today’s quiz

A friend is telling you about a movie they saw yesterday and says: “주인공이 갑자기 아무 이유 없이 범인을 용서하더라고. 앞에 아무 설명도 없었는데.” (“The main character suddenly forgives the culprit for no reason at all. There was no setup for it beforehand.”) Which sentence is the most natural thing to say next?

와, 그 장면 개연성이 높네. (wa, geu jangmyeon gaeyeonseongi nopne.)
아, 그럼 개연성이 없지. (a, geureom gaeyeonseongi eopji.)
그 배우 개연성이 크다. (geu baeu gaeyeonseongi keuda.)

Answer: 2. If a character abruptly changes their behavior with no explanation or foreshadowing beforehand, the story doesn’t connect — so 개연성이 없다 (gaeyeonseongi eopda) is the right call. Option 1 says the exact opposite, and option 3 is off because 개연성 (gaeyeonseong) attaches to stories and claims, not to a person (an actor).

Definitions and example sentences are from the National Institute of Korean Language’s Basic Korean Dictionary (krdict.korean.go.kr); that portion of this post, including our translations, is licensed under CC BY-SA 2.0 KR.