Aspiration 격음화: ㅎ + Plain Stop → Aspirated (좋다 → 조타)

Korean has an aspirated stop series — ㅋ ㅌ ㅍ ㅊ — pronounced with a strong puff of air. Aspiration (격음화, also called 축약 "contraction") is the rule that creates one of those aspirates on the fly whenever the letter ㅎ meets a plain stop. The two consonants don't stay separate; they fuse into a single aspirate, and the ㅎ disappears as an independent [h] sound. This is one of the two or three most important pronunciation rules in the language because it hits some of the highest-frequency words there are (좋다, 축하, 입학, 못하다), and — unlike tensification — it is reflected in the romanization, so for once the reading aid is on your side.

The rule: ㅎ + a plain stop → one aspirated consonant

Each plain stop has an aspirated partner, and ㅎ turns the plain one into it:

Crucially, the fusion works in either direction — ㅎ can be the batchim of one syllable meeting a stop at the start of the next, or a stop batchim meeting a following ㅎ. Both collapse into the same single aspirate.

Direction 1: ㅎ-batchim + a plain stop

Verb and adjective stems ending in ㅎ (좋다, 놓다, 넣다, 닿다) fuse their ㅎ into whatever plain stop the ending brings.

In 좋다, the ㅎ batchim of 좋 fuses with the ㄷ of 다 → ㅌ: [조타]. In 놓고, the ㅎ of 놓 fuses with the ㄱ of 고 → ㅋ: [노코]. The same stem gives 좋고 [조코], 좋지 [조치], 놓지 [노치].

Direction 2: a stop-batchim + ㅎ

Now the reverse. A syllable ending in ㄱ, ㄷ, ㅂ, or ㅈ meeting a following ㅎ fuses just the same. This direction is the one learners most often miss, because the ㅎ is sitting there at the start of the next syllable looking innocent.

축하 is 축[k] + 하 → [추카]; 입학 is 입[p] + 학 → [이팍]; 급히 is 급[p] + 히 → [그피]. A [t]-batchim works too: 맏형 (eldest brother) is 맏[t] + 형 → [마텽], and 못하다 (cannot / be bad at) is 못[t] + 하다 → [모타다].

The ㅈ direction, and ㅎ hidden in a cluster

The affricate ㅈ aspirates to ㅊ the same way. This shows up constantly in derived verbs formed with the suffix -히-, where a stem-final consonant meets that ㅎ:

• 맞히다 (to get right) → [마치다]
• 앉히다 (to seat someone) → [안치다]
• 잊히다 (to be forgotten) → [이치다]

And when ㅎ is buried inside a double batchim — ㄶ or ㅀ — it still reaches out and fuses. The other consonant of the cluster (ㄴ or ㄹ) stays; the ㅎ aspirates the following stop.

많지 is 많(ㄶ) + 지: the ㄴ stays, the ㅎ fuses with ㅈ → ㅊ, giving [만치]. Likewise 싫다 (ㅀ) → [실타], 옳지 → [올치]. For the full behavior of these ㅎ-clusters — including what happens before a vowel and before ㄴ — see ㅎ-cluster finals.

The flip side: ㅎ vanishes before a vowel (no aspiration)

Aspiration needs a stop on the other side. When a ㅎ-final stem meets a vowel ending instead, there is no stop to fuse with, so the ㅎ doesn't aspirate anything — it simply drops, and the syllables link up smoothly. This is the single most useful contrast for ㅎ-stems.

So the stem 좋- has two faces: 좋다/좋고/좋지 fuse to aspirates [조타]/[조코]/[조치], but 좋아요/좋으면 drop the ㅎ entirely to [조아요]/[조으면]. Same ㅎ, opposite fates, decided purely by whether a stop or a vowel follows. (This obligatory pre-vowel deletion is different again from the optional, casual weakening of ㅎ between voiced sounds — 전화 → [저놔] — covered in ㅎ weakening and deletion.)

The good news: romanization shows this one

Unlike tensification, aspiration is reflected in official Revised Romanization. 좋다 is jota, 놓고 is noko, 축하 is chuka, 입학 is ipak, 못하다 is motada. The romanization tracks the fusion faithfully, which means for aspiration you can — for once — read the reading aid and trust it. That is why every romanization on this page already shows a single aspirate (t, k, p, ch) rather than a stop-plus-h.

Why English speakers get this wrong

English keeps [h] as a full, breathy consonant of its own ("ahead," "behave"), so learners instinctively want to pronounce the ㅎ in 축하 as a separate Korean doesn't do that here — the ㅎ has no independent life next to a stop; it becomes the aspiration on that stop. The fix is to think of ㅎ-plus-stop not as two sounds but as one, and to let the puff of air ride on the consonant: [추카], one clean flow, not "chuk-ha." Over-correcting the other way (tensing it to [축따] or [졷따]) is just as wrong — aspiration is breathy, not clenched.

Common Mistakes

1. Keeping an audible [h] between the two consonants.

• ✗ 축하 said [축하] "chuk-ha" → ✓ [추카]
• ✗ 좋다 said [졷하] → ✓ [조타]

2. Tensing instead of aspirating. ㅎ + stop is breathy, not a tense clench.

• ✗ 좋다 said [졷따] → ✓ [조타]

3. Missing the stop-batchim-first direction. Learners catch 좋다 but forget 입학, 축하, 백화점.

• ✗ 입학 said [입학] → ✓ [이팍]
• ✗ 백화점 said [백화점] → ✓ [배콰점]

4. Aspirating where a vowel follows. Before a vowel the ㅎ drops; it does not aspirate.

• ✗ 좋아요 said [조하요] → ✓ [조아요]

5. Overlooking ㅎ hidden in a double batchim. ㄶ and ㅀ still aspirate a following stop.

• ✗ 많지 said [만지] → ✓ [만치]
• ✗ 싫다 said [실따] → ✓ [실타]

Key Takeaways

• ㅎ + a plain stop/affricate fuse into a single aspirate — ㅋ ㅌ ㅍ ㅊ — in either direction: 좋다 [조타], 놓고 [노코], 축하 [추카], 입학 [이팍], 많지 [만치].
• The ㅎ does not survive as [h] and does not tense — it becomes the breath on the consonant.
• Before a vowel, a ㅎ-stem instead simply drops the ㅎ, no aspiration: 좋아 [조아].
• Revised Romanization does show aspiration (jota, chuka, ipak) — so trust the reading aid here.