The traditional account* states that ㅈ j is derived from ㅅ s by the addition of a stroke (ㅅ而ㅈ […] 其因聲加畫—in the 15th century, ㅈ represented the affricate IPA: [ts]). However, Gari Ledyard proposes that ㅈ ts was instead borrowed from Phagspa s, ultimately from Tibetan ས s, and that it was ㅅ s which was derived by removing a stroke from ㅈ ts. Perhaps Phagspa s was used for this ts value, rather than for Korean s, by analogy with the other borrowed letters ㄱ, ㄷ, and ㅂ, from which other hangul letters were derived by removing strokes.
* Hunmin Jeongeum Haerye "Explanations and Examples of the Proper Sounds for the Instruction of the People" (1446), defining and explaining the script now known as 한글 (Hangeul, “Great script, Korean script”) in South Korea and 조선글 (joseon'geul, “Korean script”) in North Korea.
ㅈ (j, McCune-Reischauer ch)
- 지읒 (jieut), a jamo (letter) of the alphabet of the Korean writing system, hangeul.
- In the North Korean order, it is the ninth jamo. In the South Korean order, it is the thirteenth.
Derived terms 
See also 
- ス (katakana su)