2indexing radical for characters built on a small curling shape, originally meaning 'private'
Tips
usage
厶 is the proto-form of 私 (sī, private). It never appears as a free word but is the key bottom or interior element in 去, 公, 参, 能, 县, 矣 — and the upper-right of 私 itself.
history
Han Feizi quotes Cangjie: 自环者谓之厶，背厶谓之公 — what curls around itself is 'private', what turns away from it is 'public'. The character 公 (public) is literally 'opposite of 厶'.
Radical
PrivateKangxi #28
The 厶 radical, the original form of 私 and the conceptual antonym of 公 (public). A small but historically loaded slot indexing characters with a curling component: 去, 公, 参, 能, 县, 矣. Not a standalone word in modern Chinese; the meaning of 'private' has fully migrated to 私.
