Hangul syllable 찬

The surrounding word or name decides.

찬물 uses 찬, a modifier of 차다 (“cold”); 반찬 uses 饌 for food served with rice, and 찬미 uses 讚 for praise. Hanja are Chinese characters used in Korean words and names.

King Sejong's Hangul groups letters into Korean syllable blocks; 찬 follows that pattern. The system is first recorded in 1443; the explanatory Hunminjeongeum book appeared in 1446. In classical Korean writing, 讚 praised people and paintings after earlier ritual praise addressed to spirits.