Several parts combine into one character.

修 is a phonetic-semantic compound: 攸 (yōu, "to flow / wash") + 彡 (the "fine streaks" radical, indicating texture or grain). The composite reads as "to refine the grain of body and mind through washing / discipline" = to cultivate, to train, to refine, to repair. The character carries one of the most consequential concepts in East Asian thought: 修 names the lifelong project of self-cultivation, the gradual polishing of character through study, practice, and discipline. Confucianism, Buddhism, and Daoism all center on 修 as the path of becoming a moral and capable person.

Korean reading "su." 修練 (suryeon, training / discipline — used for spiritual training, martial arts, and skill development), 修養 (suyang, cultivation / cultivation of character — central Korean Confucian concept: "self-cultivation"), 修行 (suhaeng, ascetic practice / spiritual discipline — Buddhist term), 修理 (suri, repair — practical engineering use), 修飾 (susik, modification / decoration — grammar term: modifier), 必修 (pilsu, "must-cultivate" = required course / compulsory study). Korean academic vocabulary heavily uses 수.

Mandarin xiū, 1st tone. 修 (xiū), 修理 (xiūlǐ, to repair), 修改 (xiūgǎi, to revise / amend), 修养 (xiūyǎng, cultivation / refinement of character), 必修 (bìxiū, required course), 修建 (xiūjiàn, to build / construct). Modern Mandarin keeps 修 active in both spiritual and practical contexts.

Japanese on-readings split. シュウ (shū) for academic / practical: 修理 (shūri, repair — universal Japanese vocabulary), 修学旅行 (shūgaku ryokō, "study-travel" = the iconic Japanese school field trip taken in middle and high school years; a defining shared memory for Japanese students), 研修 (kenshū, training / professional development), 必修 (hisshū, required course). シュ (shu) for religious / disciplinary: 修行 (shugyō, ascetic practice / training — used for Zen monks, martial artists, and traditional craftspeople undergoing disciplined apprenticeship). Kun-reading おさめる (osameru) — 修める (osameru, "to master / complete a course of study"). The concept of 修行 carries deep weight in Japanese culture, from monastery training to mastering ramen-making.

Memory aid: 攸 (washing / refining) + 彡 (fine grain) — polishing the texture of self = cultivation, training, repair.