公开信
gōng kāi xìn · HSK 7
letter
📜 公 (public) + 开 (open) + 信 (letter) = public open letter
公开 means public/open, and 信 is letter or message. Together 公开信 is a letter written to be read publicly, often addressed to an official but published for everyone.
公 — eight 八 + private 厶
Originally an ideograph showing 八 (to divide) over 厶 (private/self), depicting the act of splitting away from selfish interest. The combination came to mean 'public' or 'fair,' the opposite of private. It later extended to senses like 'duke,' 'lord,' and 'grandfather.'
开 — two hands 廾 + door 门 (open gate)
Originally written 開, showing two hands (廾) lifting the bar (一) off a gate (門) to open it. The simplified form 开 keeps the two-hands element and drops the gate. Core meaning 'to open' extended to 'start, operate, bloom'.
信 — person 亻 + speech 言
信 combines 亻(person) with 言(speech), depicting a person standing by their words. The original sense is 'truthfulness' or 'sincerity'—what a person says can be trusted. From this it extended to 'believe,' 'trust,' and later 'message' or 'letter,' since a letter carries one's word.