通行证
tōng xíng zhèng · HSK 7
pass
🪪 通 pass-through + 行 go + 证 certificate = the certificate that lets you go through
通 (tōng) means pass through, 行 (xíng) means go or travel, and 证 (zhèng) is a certificate or proof. Stacked together they name the document that authorizes you to go through a checkpoint, hence a pass or safe conduct.
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'.
行 — crossroads pictograph (left 彳 + right 亍)
行 originally pictured a four-way crossroads in oracle bone script, with two paths meeting. From 'road' it extended to 'walk, go, travel,' and then to 'a row, line' or 'business firm' (read háng). The two halves 彳 and 亍 are the split sides of that ancient crossroads.
证 — speech radical 讠 + 正 (correct/upright)
证 is a semantic-phonetic compound. The speech radical 讠 (言) signals it relates to words or testimony, while 正 (zhèng, 'upright/correct') gives the sound and hints at 'verifying truth.' Originally written 證, it meant to testify or prove; today it means evidence, certificate, or to prove.