信箱
xìnxiāng · HSK 5
mailbox
📬 信 (letter) + 箱 (box) = letter-box
信 means letter or message (亻person + 言 speech = trusted word). 箱 means box or case (⺮ bamboo radical, since old storage boxes were woven from bamboo). Together: the box where letters are kept.
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.
箱 — bamboo radical 竹 + 相 (xiāng) phonetic
A semantic-phonetic compound. The bamboo radical 竹 on top signals the original meaning: a box or chest woven from bamboo or made of wood. The component 相 below supplies the sound 'xiāng'. Over time the meaning broadened from bamboo containers to boxes and cases of any material.