通信
tōngxìn · HSK 3
correspond
📬 通 = through + 信 = letter/message: messages going through
通 means to pass through or connect; 信 means letter or trustworthy message. Together they describe correspondence — sending word back and forth, originally by mail and now by any channel.
通 — 辵 (辶) walk + 甬 yǒng (phonetic)
通 is a semantic-phonetic compound. The 辶 (chuò) component means 'walk' or 'movement', giving the meaning of going through or passing. 甬 (yǒng), originally depicting a hanging bell or a path, supplies the sound. Together they convey 'to pass through, communicate, connect'.
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.