夬

in I Ching (주역 周易), the 43rd hexagram Guài (夬卦), formed by ☱ (兌, Lake) above and ☰ (乾, Heaven) below;

also refers to a thumb-ring or archery release aid (깍지, for drawing the bowstring);

Pictograph / ideogrammic origin:

Ancient form shows a hand with a special thumb-ring device for drawing a bowstring.

Later associated with the act of dividing, separating, or decisively cutting.

Rare in modern daily use except in classical texts (I Ching), or as a phonetic in other characters.

夬卦 (쾌괘) — the Guài hexagram (No. 43 of the 64 hexagrams)

Extended phonetic role: appears in compounds where it provides either 쾌 (快 “joyful,” 筷 “chopsticks”) or 결 (決 “decide,” 缺 “lack”).

In traditional rime dictionaries (운서 韻書), placed under the Guài rime group (夬韻).

In Sino-Korean reading, ᄏ [kʰ] initial is rare and appears only in this rime group. Thus, 夬 has dual readings:

본음 (original sound): 괘 (due to its voiceless initial)

속음 (secondary sound): 쾌, peculiar to Korean phonological history.

Among characters with the Sino-Korean reading 쾌, only 快 (“joyful, pleasant”) is widely used in contemporary vocabulary.

叏 is an older graphic variant retaining the archaic shape.