|Positive/"light"/Yang Vowels||ㅏ (a)||ㅑ (ya)||ㅗ (o)||ㅛ (yo)|
|ㅐ (ae)||ㅘ (wa)||ㅚ (oe)||ㅙ (wae)|
|Negative/"heavy"/Yin Vowels||ㅓ (eo)||ㅕ (yeo)||ㅜ (u)||ㅠ (yu)|
|ㅔ (e)||ㅝ (wo)||ㅟ (wi)||ㅞ (we)|
|Neutral/Centre Vowels||ㅡ (eu)||ㅣ (i)||ㅢ (ui)|
Traditionally, the Korean language has had strong vowel harmony; that is, in pre-modern Korean, as in most Altaic languages, not only did the inflectional and derivational affixes (such as postpositions) change in accordance to the main root vowel, but native words also adhered to vowel harmony. It is not as prevalent in modern usage, although it remains strong in onomatopoeia, adjectives and adverbs, interjections, and conjugation. There are also other traces of vowel harmony in Korean.
There are three classes of vowels in Korean: positive, negative, and neutral. The vowel eu is considered partially a neutral and negative vowel. The vowel classes loosely follow the negative and positive vowels; they also follow orthography. Exchanging positive vowels with negative vowels usually creates different nuances of meaning, with positive vowels sounding diminutive and negative vowels sounding crude.
- 퐁당퐁당 (pongdangpongdang) and 풍덩풍덩 (pungdeongpungdeong), light and heavy water splashing
- Emphasised adjectives:
- 노랗다 (norata) means plain yellow, while its negative, 누렇다 (nureota) means very yellow
- 파랗다 (parata) means plain blue, while its negative, 퍼렇다 (peoreota) means deep blue
- Particles at the end of verbs:
- 잡다 (japda) (to catch) → 잡았다 (Jabatda) (caught)
- 접다 (jeopda) (to fold) → 접었다 (Jeobeotda) (folded)
- 아이고 (aigo) and 어이구 (eoigu) expressing surprise, discomfort or sympathy
- 아하 (aha) and 어허 (eoheo) expressing sudden realization and mild objection, respectively