坑道|こうどうkoudou[0]heiban (flat)

1. nountunnel; (mining) gallery; level; shaft; pit

• RelatedトンネルNeutralLoanword for tunnel, the everyday default; mainly for transport routes through mountains or under water, while 「坑道」 covers passages dug in mines or for military use.
• Related隧道すいどうWrittenWritten, old-fashioned word for tunnel; it can also mean a passage leading to a burial chamber. In modern usage 「トンネル」 is the normal choice.

Use 「坑道」 for passages dug underground in mines or for military purposes, as in 「炭鉱の坑道」. For transport tunnels the everyday word is 「トンネル」; 「隧道」 is an old written term now rarely used.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 地下ちかに設もうけられた通路つうろ。地下ちか道どう。
2. 鉱山こうざんなどの坑内こうないに設もうけられた通路つうろ。