Definition
In Korean phonology, liaison (known as yeoneum) is the phonetic rule where a final consonant (받침, batchim) smoothly shifts to become the opening sound of the following vowel-initial syllable (with minor exceptions such as 'ㅇ' and 'ㅎ'). It is a fundamental sound rule that minimizes tongue and mouth effort, creating natural, flowing speech.
Final Consonants Move to Empty Seats
On a crowded subway, if the seat next to you empties out, you naturally slide over to sit more comfortably. Spoken Korean works the exact same way: whenever a sound spots an empty slot ahead, it naturally shifts over to fill it. A final consonant (받침, batchim) anchored at the bottom of a syllable will glide forward whenever the following syllable begins with an open, vowel-led sound.
In Hangul, the circular letter 'ㅇ' (ieung) written at the start of a syllable is actually a silent placeholder. Because a Hangul syllable block cannot be written with just a solitary vowel, 'ㅇ' serves as a temporary empty chair. When a word ending in a consonant meets an initial vowel, your vocal tract saves energy by pushing that final consonant right up into the open seat.
For example, reading the phrase 옷이 (osi, 'clothes [subject]') sounds like [오시] (o-si), and 밥을 (babeul, 'rice [object]') becomes [바블] (ba-beul). Pronouncing each syllable separately requires your tongue and lips to tense up on every block, but sliding directly into the empty sound slot lets spoken words flow like water.
A Closer Look: Single vs. Double Final Consonants
The way liaison unfolds varies depending on the type of consonant and the nature of the following word. When a syllable ends in a double consonant (겹받침, gyeopbatchim) and is followed by a grammatical particle or verb ending that starts with a vowel, both consonants do not jump over together. Instead, the first consonant stays put, and only the second consonant moves to the next syllable.
For instance, in 닭이 (dalgi, 'chicken [subject]'), the first consonant 'ㄹ' remains in the bottom slot while 'ㄱ' carries over, sounding like [달기] (dal-gi). Similarly, 값이 (gapsi, 'price [subject]') keeps 'ㅂ' and carries over 'ㅅ', which tenses into a reinforced sound pronounced [갑씨] (gap-ssi). This division lets the tongue articulate two distinct consonants without stumbling. However, combinations like 'ㄶ' and 'ㅀ' are exceptions: the 'ㅎ' sound is dropped and the first consonant shifts over, turning 않아 (ana, 'not do') into [아나] (a-na) and 싫어 (sireo, 'dislike') into [시러] (si-reo). Single consonants have exceptions too: the velar nasal 'ㅇ' (ng) never carries over (e.g., 강이 [gang-i, 'river [subject]']), and 'ㅎ' simply drops before vowels (e.g., 좋아 [jo-a, 'good/like']).
When the following word carries independent lexical meaning and begins with vowels like 'ㅏ' (a), 'ㅓ' (eo), 'ㅗ' (o), 'ㅜ' (u), or 'ㅟ' (wi), standard Korean adds one extra step. Instead of sliding over immediately as [오산] (o-san), the phrase 옷 안 (ot an, 'inside the clothes') first simplifies its final consonant to its representative sound 'ㄷ' (d) before moving, sounding like [오단] (o-dan). The same principle applies inside compound words like 겉옷 [거돋] (geodot, 'outerwear'). Grammatical endings trigger instant liaison, but words with concrete semantic meaning require consonants to neutralize first (Standard Korean Pronunciation Rules, Article 15). Furthermore, before vowels like 'ㅣ' (i) or iotized vowels like 'ㅑ' (ya), an inserted 'ㄴ' (n) sound often emerges, turning 옷 입다 (ot ipda, 'put on clothes') into [온닙따] (on-nip-tta). Exceptionally, everyday words like 맛있어 (masisseo) officially recognize both [마싣따] and [마딛따] (masitda/maditda) as standard speech.
Why Spellings Stay While Sounds Shift
If pronunciation shifts so naturally, why not spell words phonetically as [오시] (o-si) or [바블] (ba-beul) instead of 옷이 and 밥을? Writing purely by sound would make it nearly impossible for readers to decipher the core meaning of words at a glance.
If spelling changed along with every liaison, the single noun 옷 (ot, 'clothes') would morph unpredictably into 옷 (ot), 오시 (o-si), 오슬 (o-seul), or 오세 (o-se) depending on what particle follows. Readers would have to pause constantly to deduce whether each variant refers to clothing or an entirely different word.
That is why standard Hangul orthography dictates that while spoken words should flow comfortably, written words must retain their base forms so their original meanings remain instantly clear. Korean liaison harmonizes the ear and the eye: it produces the smoothest acoustic rhythm for listeners while letting readers grasp sentence meaning in an instant.
Common misconceptions
When liaison occurs, the written spelling must also change to match the pronunciation.
Liaison applies strictly to spoken pronunciation. In writing, original base forms such as 옷이 (osi, 'clothes') and 꽃을 (kkocheul, 'flower') are preserved to keep word meanings distinct and legible.
Where you meet it
Saying 달이 밝다 (dari bakda, 'the moon is bright'), where 달이 (dal-i) flows into [다리] (da-ri)
Saying 꽃을 심다 (kkocheul simda, 'to plant a flower'), where 꽃을 (kkot-eul) transitions into [꼬츨] (kko-cheul)
Saying 흙에 묻다 (heulge mutda, 'to get covered in soil'), where the double consonant splits to sound like [흘게] (heul-ge)
In one sentence
When a final consonant meets a vowel-initial syllable in Korean, it slides forward into the empty slot for smoother speech, while written spellings stay unchanged to keep meanings instantly recognizable.