Korean Sai Siot: Sounds, Rules and Examples

Korean sai siot (사이시옷, "the in-between ㅅ") is a linking ㅅ written under the first part of some compound nouns, such as 바닷가 (seaside) and 나뭇잎 (leaf). The ㅅ is never said as [s]. It signals one of three sound changes: a tense consonant, an added [ㄴ], or an added [ㄴㄴ].

What you'll learn

• Say 냇가, 바닷가, 콧날 and 나뭇잎 with the correct sound change.
• Sort a sai-siot compound into one of the three sound groups by looking at the second part.
• Decide whether a new compound should be written with sai-siot, using four checks.
• Name the six Sino-Korean words that keep sai-siot.

Prerequisite: Tensification, because the most common sai-siot sound is a tense consonant. It also helps to know Korean n-insertion. Estimated time: 30 minutes.

What Is Korean Sai Siot?

Korean sai siot is a spelling device that shows a sound change at the seam of a compound noun. A compound noun is one noun made from two nouns, like English "seaside" from "sea" and "side". When Korean joins 바다 (sea) and 가 (edge), speakers do not say [바다가]. They say [바다까], with a tense ㄲ. The spelling adds a ㅅ under 다 to show that something happens at the join.

The name explains the job. 사이 means "between", and 시옷 is the name of the letter ㅅ. So 사이시옷 is "the ㅅ in between". It belongs to the first syllable as a final consonant (batchim), but it is not part of either word on its own. 바다 alone has no ㅅ, and 가 alone has no ㅅ.

The three rows show three different results from the same written ㅅ. That is the central idea of this lesson: the letter is the same, but the sound depends on what follows. The next section explains why this trips up English speakers.

Why English Speakers Struggle with Sai-Siot

English speakers struggle with sai-siot because English spelling has trained them to pronounce every written letter. A learner who sees 바닷가 tends to say "ba-dat-ga" with a clear [t] or even "ba-das-ga" with an [s]. Neither matches Korean speech.

English also has no tense consonants. The tense ㄲ in [바다까] is made with a tight throat and no puff of air, a sound English does not use to tell words apart. So the learner both adds a sound that is not there (the [s]) and misses the sound that is there (the tension).

A third problem is that English compounds do not change their sounds. "Rain" plus "water" is still "rainwater". Korean 비 (rain) plus 물 (water) becomes 빗물 [빈물], with a new [ㄴ]. The learner has no model for a compound that grows an extra consonant. The fix is to learn the sound first and the spelling second, which is the order of the next sections.

How Is Sai Siot Pronounced?

Sai siot is pronounced in one of three ways, and the first consonant of the second part decides which. Standard Pronunciation Rules (표준 발음법) Article 30 sets out all three.

The table below gives 12 compounds, four in each group. Learn them as sets, because each set teaches the ear one pattern.

Group 1: a Tense Sound before ㄱ, ㄷ, ㅂ, ㅅ, ㅈ

Before a plain ㄱ, ㄷ, ㅂ, ㅅ or ㅈ, sai-siot makes that consonant tense: ㄱ → [ㄲ], ㄷ → [ㄸ], ㅂ → [ㅃ], ㅅ → [ㅆ], ㅈ → [ㅉ]. The ㅅ itself is silent in the main form. 햇살 is [해쌀], not [햇살] or [해살].

Article 30 also allows a second form in which the ㅅ is heard as a short, closed [ㄷ]: 냇가 [낻까], 햇살 [핻쌀], 콧등 [콛뜽]. Both forms are standard. The tense-only form is the main one, and it is the one in the audio on this page.

This group is the same tense sound you met in Korean tensification. The difference is that here the spelling warns you in advance.

Group 2: [ㄴ] before ㄴ and ㅁ

Before ㄴ or ㅁ, sai-siot sounds as [ㄴ]. Two steps produce this. First, the ㅅ in the final position is read as [ㄷ], the way any final ㅅ is. Then [ㄷ] becomes [ㄴ] before a nasal, a rule called nasalization. So 콧날 goes 콛날 → [콘날], and 빗물 goes 빋물 → [빈물].

A good test: the ㄴ in 콧날 should feel long, like the "nn" in English "unnamed". If you hear a [t] or an [s], the nasal step has not happened.

Group 3: [ㄴㄴ] before 이, 야, 여, 요, 유

Before a second part that starts with 이 (or 야, 여, 요, 유), sai-siot sounds as [ㄴㄴ]. Three rules run in a row. The ㅅ is read as [ㄷ]. An extra [ㄴ] is added before the 이 sound, which is Korean n-insertion. Then [ㄷ] becomes [ㄴ] before that new [ㄴ]. 나뭇잎 goes 나묻 + 닙 → [나문닙].

깻잎 is a useful anchor, because many learners already know the word from Korean food. Its Revised Romanization, kkaennip, shows both ㄴ sounds. With the sounds clear, the spelling rule makes sense.

When Is Sai Siot Written?

Sai siot is written only when four conditions are all true. Hangul Orthography (한글 맞춤법) Article 30 states them. Run the checks in this order on any compound noun.

1. It is a compound of two nouns, not a word plus a suffix. 해님 (the sun, personified) is 해 + the suffix -님, so it has no sai-siot.
2. At least one part is a native Korean word. Native + native (바닷가), native + Sino-Korean (귓병, ear disease, [귀뼝]) and Sino-Korean + native (전셋집, a house rented on a lump-sum deposit, [전세찝]) all qualify. Two Sino-Korean parts do not, except for six words.
3. The first part ends in a vowel. 바다 ends in ㅏ, so ㅅ can go under 다. 길 (road) ends in ㄹ, so 길가 (roadside) [길까] has no sai-siot, even though it is tense.
4. A sound change happens at the seam. The second consonant becomes tense, or an [ㄴ] or [ㄴㄴ] appears. 머리말 (preface) is said [머리말], with no change, so it is written without ㅅ.

One more limit applies. If the second part already starts with a tense or aspirated consonant, nothing can be added, so nothing is written: 위쪽 (the upper side), 뒤풀이 (an after-party). Loanword parts also do not take sai-siot, so 피자집 (pizza place) is written without it.

The full spelling rule, with more word lists, is on the sai-siot spelling page under Korean spelling. The next question shows the fourth check and this extra limit at work in one pair.

Why Do 윗니 and 위쪽 Differ in Spelling?

윗니 (upper teeth) and 위쪽 (the upper side) differ because only one of them has a sound change at the seam. 위 + 니 is said [윈니], with an added [ㄴ], so a ㅅ is written. 위 + 쪽 already starts with the tense ㅉ, so no sound is added and no ㅅ is written.

A precise note: the spelling of 윗- and 위- is formally set by the Standard Language Regulations (표준어 규정), Article 12, which treats 윗- as the standard form of the "upper" prefix and 위- as the form before tense and aspirated consonants. The result matches the sai-siot logic exactly, so you can learn both with one rule. The pair also explains a common native misspelling, 윗층, which the standard rejects.

Which Sino-Korean Words Keep Sai Siot?

Six Sino-Korean words keep sai siot, and Hangul Orthography Article 30 lists exactly these six. A Sino-Korean word is one built from Chinese-origin morphemes (hanja). Every other compound of two Sino-Korean parts is written without ㅅ, even when it is tense.

The contrast that shows the rule best is 횟수 against 개수 (個數, the number of items). Both end in 수 (數, number) and both are said with a tense [쑤]: [회쑤] and [개쑤]. Only 횟수 is on the list, so only 횟수 gets the ㅅ. 초점 (焦點, focus) [초쩜] and 대가 (代價, price paid) [대까] follow the same no-ㅅ pattern. For daily life, 숫자 and 횟수 are the two you will see most.

Is There a Sai-Siot Sound without the Letter?

Yes. Many compounds show the same tense sound with no ㅅ written, because one of the four spelling checks fails. The sound change is a pronunciation fact, and sai-siot is only its spelling.

The practical lesson is that you cannot predict every tense compound from spelling. Spelling helps when ㅅ is there. When it is not, a compound may still be tense, and the dictionary pronunciation in brackets, for example in the 표준국어대사전 (Standard Korean Language Dictionary), is the safe reference. A worked example now puts the steps together.

Worked Example: 냇가

Follow these steps to read 냇가 (stream bank) aloud.

1. Split the compound. 냇가 = 내 (stream) + ㅅ + 가 (edge). The ㅅ under 내 is sai-siot, because 내 alone has no final consonant.
2. Look at the second part. 가 starts with plain ㄱ, one of ㄱ, ㄷ, ㅂ, ㅅ, ㅈ. So this is Group 1, the tense group.
3. Make the consonant tense. ㄱ becomes [ㄲ]. The ㅅ is silent in the main form.
4. Say it. [내까]: a short 내, then a tight, unaspirated 까 with no puff of air.
5. Know the variant. [낻까], with a brief closed [ㄷ] before 까, is also standard.

You will know it worked when your 냇가 rhymes with 바닷가 [바다까] at the end, and a hand in front of your mouth feels almost no air on 까. If you hear "nat-ga" or "nas-ga", the ㅅ is being pronounced as a letter. Practise this word, then compare it with 냇물 (stream water) [낸물], which belongs to Group 2.

Common Mistakes with Korean Sai Siot

Mistake 1: saying the ㅅ as [s]. Learners often say 바닷가 as "ba-das-ga". Actually the ㅅ is never [s], because a final ㅅ is read as [ㄷ] or is silent. Say [바다까].

Mistake 2: reading every sai-siot as tense. Learners who know 냇가 [내까] often say 콧날 as [코딸] or [코날]. Actually the second part decides the sound. Before ㄴ the result is [콘날].

Mistake 3: forgetting the double ㄴ. Learners often say 나뭇잎 as [나무입] or [나무닙]. Actually both the sai-siot and the n-insertion appear, giving [나문닙]. Count two ㄴ sounds.

Mistake 4: expecting ㅅ after a consonant. Learners who hear the tense sound in 길가 or 등불 sometimes expect a sai-siot in the spelling. Actually a first part that ends in a consonant cannot take sai-siot. The sound is still tense: [길까], [등뿔].

Mistake 5: writing ㅅ in every Sino-Korean compound. Learners who see 횟수 sometimes write 갯수 for 개수. Actually only six Sino-Korean words keep sai-siot, and 개수 is not one of them.

Each mistake comes from treating sai-siot as a sound instead of a signal. The practice set below rehearses all five.

Practice and Answer Key

Exercise 1. Write the spoken form (main form only).

1. 햇살
2. 빗물
3. 깻잎
4. 콧등
5. 뒷일

Exercise 2. Which group does each word belong to: tense, [ㄴ] or [ㄴㄴ]?

1. 뱃머리
2. 바닷가
3. 베갯잇
4. 아랫니

Exercise 3. Should the compound be written with sai-siot? Answer yes or no and give the reason.

1. 해 + 님 (the sun, personified)
2. 비 + 물 (rainwater)
3. 초 + 점 (焦點, focus)
4. 위 + 층 (upper floor)

Answers.

Exercise 1: 1 [해쌀], 2 [빈물], 3 [깬닙], 4 [코뜽], 5 [뒨닐].

Exercise 2: 1 [ㄴ] ([밴머리]), 2 tense ([바다까]), 3 [ㄴㄴ] ([베갠닏]), 4 [ㄴ] ([아랜니]).

Exercise 3: 1 no: -님 is a suffix, so 해님. 2 yes: an [ㄴ] appears, so 빗물. 3 no: two Sino-Korean parts, not on the list of six, so 초점. 4 no: ㅊ is already aspirated, so 위층.

If you missed two or more in Exercise 1, replay the three audio groups once each and say the words with the speaker.

Where to Go Next

Sai-siot sits where three rules meet, so review whichever one felt weakest: Korean tensification for Group 1, nasalization for Group 2, and Korean n-insertion for Group 3. The words that refuse n-insertion are in Korean n-insertion exceptions.

When sai-siot feels easy, continue with Korean sound changes between words, which applies the same rules across word spaces. The full set of rules is listed on the Korean Sound Change Rules page.

This lesson covers sai-siot in Standard Korean as used in South Korea. It does not cover North Korean spelling, regional pronunciations, or the full word lists of Article 30. Those belong to the spelling pages and a dictionary.

In short, Korean sai siot is a written ㅅ that marks a sound change at the seam of a compound, and the second part decides whether you hear a tense consonant, [ㄴ] or [ㄴㄴ].

Frequently Asked Questions

Why is 바닷가 spelled with ㅅ? 바닷가 (seaside) is a compound of two native words, 바다 (sea) and 가 (edge). 바다 ends in a vowel, and in the compound the ㄱ of 가 is said tense, [바다까]. Those three facts meet the conditions of Hangul Orthography Article 30, so the ㅅ is written to mark the tense sound.

How is 나뭇잎 pronounced? 나뭇잎 (leaf) is pronounced [나문닙]. The sai-siot is read as [ㄷ], an extra ㄴ is added before 잎 because 잎 starts with an 이 sound, and the [ㄷ] then becomes [ㄴ] before that ㄴ. The final ㅍ of 잎 is said [ㅂ]. Revised Romanization writes namunnip.

Is sai-siot hard to remember? The sound side is easy, because you can hear it in every compound. The spelling side is harder, and Korean writers also misspell words such as 머리말 and 위층. A safe method is to learn compounds as whole words with their audio and check a dictionary when you write a new one.

Do all compounds use sai-siot? No. Most compounds have no sai-siot. It is missing when the first part ends in a consonant (길가), when both parts are Sino-Korean (초점, 개수), when the second part already starts with a tense or aspirated consonant (위쪽), and when no sound change happens (머리말).

Can I pronounce 냇가 as [낻까]? Yes. Standard Pronunciation Rules Article 30 gives [내까] as the main form and also allows [낻까], where the sai-siot is heard as a short closed [ㄷ] before the tense ㄲ. Both are standard. Most learners find [내까] easier, and both are understood everywhere in Korea.

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