隧道
suìdào · HSK 7
tunnel
🚇 隧道 = 隧 (underground passage) + 道 (road/way) — a road that bores through
道 is the same dào you meet in 知道 and 道路, meaning road or way. Pair it with 隧 (a passage dug through earth) and you get the road that runs underground: a tunnel. Sound: sway-dao, two falling tones.
道 — 辶 (walk) + 首 (head)
Originally a compound of 辶 'walk/movement' and 首 'head', depicting a path one walks while looking ahead. The literal sense 'road, way' extended metaphorically to 'method, doctrine, the Way (Dao)'. This philosophical meaning became central in Daoist and Confucian thought.