be sad
惻 centers on a deep, heartfelt sadness or grief. The meaning 'be sad' captures this emotional state directly.
惻 combines the heart radical 忄 with 則, which likely contributes the sound. The heart component points to an emotional state, consistent with sadness.
The heart radical 忄 beside 則 suggests a heart weighed down by rules or order, leading to sadness. Imagine a heart constrained by strict rules, feeling deep sorrow.
For ソク, picture a heart so sad it feels like a sock soaked in tears: sock -> ソク, and the heart is heavy with grief.