Korean Verb Stem Tensification: Sounds, Rules and Examples

Korean verb stem tensification is the rule that makes an ending starting with ㄱ, ㄷ, ㅅ or ㅈ tense when it follows a verb or adjective stem ending in ㄴ or ㅁ. 신고 (wearing, then) is [신꼬], 앉다 (to sit) is [안따] and 닮다 (to resemble) is [담따]. Nouns and the suffix -기- do not tense.

What you'll learn

• Tense the ending in 신고, 앉다, 삼고, 닮다 and 껴안지.
• Leave 안기다 and 감기다 plain, and explain why.
• Tell the verb form 신고 [신꼬] from the noun 신고 [신고] by grammar, not spelling.
• Conjugate 신다 and 앉다 aloud in six common forms.

Prerequisites: the always-on rule in Korean Tensification After Batchim, and the idea of a verb stem. Estimated time: 25 minutes.

What Is Korean Verb Stem Tensification?

Korean verb stem tensification is the second trigger in the tensification rules: a plain ㄱ, ㄷ, ㅅ or ㅈ at the start of a grammatical ending turns into its tense partner ㄲ, ㄸ, ㅆ or ㅉ when the verb or adjective stem before it ends in ㄴ or ㅁ. A tense consonant is made with a tight throat and almost no breath.

Article 24 of the Standard Pronunciation Rules, published by the National Institute of Korean Language (국립국어원), states the rule and gives examples such as 신고 [신꼬], 껴안다 [껴안따], 앉고 [안꼬], 삼고 [삼꼬], 더듬지 [더듬찌] and 닮고 [담꼬]. Article 25 adds stems ending in ㄼ and ㄾ, such as 넓게 [널께].

What Counts as a Verb Stem?

A verb stem is the part of a Korean verb or adjective that stays when you remove -다 from the dictionary form. 신다 (to wear on the feet) has the stem 신-; 앉다 (to sit) has 앉-; 젊다 (to be young) has 젊-. Korean adjectives conjugate like verbs, so their stems count too.

An ending is the grammatical piece that attaches to the stem: -고 (and then), -다 (dictionary form), -지 (used in 지 마세요, don't), -게 (so that), -습니다 (formal statement). Verb stem tensification happens only at this join, where a stem ending in ㄴ or ㅁ meets an ending beginning with ㄱ, ㄷ, ㅅ or ㅈ.

That definition already hints at the main difficulty: the trigger is grammatical, not just a sound, and grammar is invisible in spelling.

Why Learners Miss Verb Stem Tensification

Learners miss verb stem tensification because nothing in the sound alone predicts it. With Korean Tensification After Batchim, a final stop always tenses the next consonant, so the ear can learn a pattern. After ㄴ or ㅁ, there is no such pattern: 신고 (wearing, then) is [신꼬], but 신고 (a report) is [신고], and 친구 (friend) is [친구].

English gives no help either. English speakers link a final n or m smoothly into the next syllable, as in "income" or "sunglasses", and the consonant after n is never made tighter. Carried into Korean, that habit gives [신고] for the verb form, which sounds like the noun "report".

A second source of trouble is nasalization, which learners meet first. Nasalization teaches that ㄴ and ㅁ change other sounds into nasals. Verb stem tensification works in the other direction: ㄴ and ㅁ stay as they are and make the next consonant tense. Seeing the rule written out as a condition table makes it easier to apply.

When Does a Verb Stem Tense the Next Consonant?

A verb stem tenses the next consonant when three conditions are all true: the word is a verb or adjective, its stem ends in the sound [ㄴ] or [ㅁ], and the ending starts with ㄱ, ㄷ, ㅅ or ㅈ. If any condition fails, the ending stays plain.

Double batchim count by the sound they keep. In 앉다, ㄵ is said [ㄴ], so 앉- behaves exactly like 안-; the ㄵ lesson on double batchim shows how ㄵ reduces. In 닮다, ㄻ is said [ㅁ], explained in the ㄻ batchim lesson.

Note what is missing from the table: stems ending in plain ㄹ, such as 알다 (to know), do not tense: 알고 is [알고]. Stems in ㄶ, such as 많다 (to be many), follow a different rule, aspiration: 많고 is [만코]. Once the stem passes the test, the next question is which endings take part.

Which Endings Are Affected?

Every ending that starts with ㄱ, ㄷ, ㅅ or ㅈ is affected. Endings starting with ㅂ are not listed in the rule, because standard Korean has almost no endings that start with ㅂ after a consonant stem. The table uses 신다 (to wear on the feet) as the model verb.

Two details in the table are easy to miss. In 신습니다, only the ㅅ of -습- tenses; the ㅂ before ㄴ then nasalizes, giving [신씀니다]. And the nominalizer -기, which turns a verb into a noun-like "the act of", is an ending, so it tenses: 신기 [신끼]. That -기 must not be confused with the suffix -기- in the next section.

Endings that start with a vowel or with ㄴ never tense: 신어요 (I wear) is [시너요] by liaison, and 신는 (that wears) is [신는]. With the endings sorted, the exceptions become the last check.

Which Verbs Do Not Tense?

Verbs formed with the passive or causative suffix -기- do not tense, even when the stem ends in ㄴ or ㅁ. A suffix is a piece that builds a new verb, unlike an ending, which only changes the form of a verb. Article 24 names this exception explicitly, with examples such as 안기다, 감기다, 굶기다 and 옮기다.

The contrast between 신기 [신끼] (the act of wearing) and 신기다 [신기다] (to put shoes on someone) is the clearest test of the exception: the same 신 + 기, two grammatical roles, two pronunciations. The full grammar of these verbs is covered under korean passive verbs. Telling a verb ending from a suffix is one form of a wider skill: telling words apart by class.

How Do You Tell a Noun from a Verb?

You tell a noun from a verb by its place in the sentence and by what attaches to it. A noun takes particles such as 을, 이 or 도, or combines with 하다; a verb stem takes endings and ends a clause. Only the verb triggers tensification.

The 안다 pair is worth a second look. In 안다 (knows), the ㄴ is not part of the stem: the stem is 알-, its ㄹ drops, and ㄴ comes from the ending -ㄴ다. Because the stem does not end in ㄴ, the ㄷ stays plain. An expert habit: when a verb form ends in ㄴ다 or ㄴ, ask whether that ㄴ belongs to the stem or to the ending before you decide. One fully worked sentence puts all of this together.

Worked Example: 신고

The sentence is 신발을 신고 나가요 (I put on my shoes and go out). Work out how to say 신고.

1. Find the word class. 신발을 is a noun with the object particle 을. 신고 comes after the object and links to 나가요, so it is a verb form.
2. Find the stem and the ending. The dictionary form is 신다; the stem is 신-, and the ending is -고 (and then).
3. Check the stem final. 신- ends in ㄴ. Condition met.
4. Check the ending. -고 starts with ㄱ, one of ㄱ ㄷ ㅅ ㅈ. Condition met.
5. Check for -기-. There is no passive or causative suffix. Tense it: [신꼬].
6. Say the sentence. 신발을 links by liaison to [신바를], and 나가요 has no change: [신바를 신꼬 나가요].

You'll know it worked when the 꼬 in 신고 sounds as tight as the ㄲ in 꼬리 (tail), with almost no breath. Note that 신발 (shoes), a noun, stays [신발] with a plain ㅂ, even though it starts with the same 신.

Conjugation Drill: 신다 and 앉다

The drill below gives the six forms learners use most. Say each row aloud, then cover the last two columns and test yourself. Rows with a vowel ending show what happens when the rule does not apply.

In 앉아요 and 앉으세요, the ㅈ of ㄵ moves into the next syllable by liaison, so [안자요] and [안즈세요] keep both letters. In every consonant ending, only the ㄴ survives and the ending tenses. Verb pages in the Korean verbs hub show full conjugations for more stems.

Common Mistakes with Verb Stem Tensification

Learners often tense nouns. They say 신고 (a report) as [신꼬]. Actually, only verb and adjective stems trigger the rule, because Article 24 is about endings. Fix: check whether the word takes particles or endings.

Learners often tense -기- verbs. They say 안기다 as [안끼다]. Actually, -기- is a suffix that builds a new verb, and Article 24 lists it as an exception. Fix: if adding -기- changes the meaning to "be done" or "make someone do", keep it plain.

Learners often miss the rule in double batchim. They see ㄵ in 앉다 and say [안다] or [안자]. Actually, ㄵ reduces to [ㄴ] before a consonant and then tenses the ending. Fix: reduce first, then apply the rule.

Learners often apply it after ㄴ endings. They say 간다 (goes) as [간따]. Actually, the ㄴ of 간다 belongs to the ending -ㄴ다, not to the stem 가-. Fix: find the dictionary form first.

Practice and Answer Key

Exercise 1. Write the spoken form.

1. 안고 (hugging, then)
2. 삼다 (to make into)
3. 젊지 (young, as in 젊지 않다)
4. 얹고 (putting on top, then)
5. 넓게 (widely)

Exercise 2. Tense or plain? Give the spoken form and the reason.

1. 남기다 (to leave behind)
2. 감고 (washing hair, then)
3. 신고하다 (to report)

Answers.

Exercise 1: 1 [안꼬]. 2 [삼따]. 3 [점찌]. 4 [언꼬]. 5 [널께].

Exercise 2: 1 plain, [남기다], because -기- is a causative suffix. 2 tense, [감꼬], because -고 is an ending after the stem 감-. 3 plain, [신고하다], because 신고 is a noun combined with 하다.

Where to Go Next

Continue with Sino-Korean tensification, the third trigger, which tenses ㄷ ㅅ ㅈ after ㄹ in words built from Chinese characters, as in 갈등 [갈뜽]. Every trigger is collected in the Tensification section.

This lesson covers Standard Korean as described in Articles 24 and 25. It does not cover tensification after the future modifier -(으)ㄹ, in compound nouns, or the vowel-length marks that dictionaries add to some of these words, such as [신ː꼬]. In short, Korean verb stem tensification needs one question before you speak: is this a verb stem in ㄴ or ㅁ followed by an ending in ㄱ, ㄷ, ㅅ or ㅈ, with no -기- in between?

Frequently Asked Questions

Is 신고 shingo or shinkko? It depends on the word. The verb form 신고 (wearing, then) is said [신꼬], close to shin-kko, because -고 follows the verb stem 신-. The noun 신고 (a report) is said [신고], close to shin-go. Revised Romanization writes both as singo, because it never marks tensification, so only the grammar tells them apart.

Why is 안기다 not tense? 안기다 (to be hugged) is not tense because -기- is a passive suffix, not an ending. Article 24 of the Standard Pronunciation Rules tenses endings only and names the passive and causative -기- as an exception. So 안기다 is [안기다], while 안고 (hugging, then), with the ending -고, is [안꼬].

Does 가다 tense after 안? No. In 안 가요 (I am not going), 안 is a separate negation word, not a verb stem, so the ㄱ of 가요 stays plain: [안가요]. The rule needs a verb or adjective stem ending in ㄴ or ㅁ, followed directly by an ending. A word that merely ends in ㄴ, such as 안, does not trigger it.

What about 먹는? 먹는 is a different rule. The stem 먹- ends in ㄱ, not ㄴ or ㅁ, and the ending -는 starts with ㄴ, not with ㄱ ㄷ ㅅ ㅈ. A final ㄱ before ㄴ becomes the nasal [ㅇ], so 먹는 is said [멍는]. Verb stem tensification never applies to endings that start with ㄴ.

Does verb stem tensification happen with -아요 and -어요? No. Endings that start with a vowel, such as -아요, -어요 and -으면, cannot tense, because there is no consonant to tense. The final consonant moves into the next syllable instead, a rule called liaison: 신어요 (I wear) is [시너요], and 앉아요 (I sit) is [안자요].