空洞[kuudou] cave
空洞化[kuudouka] making hollow
鐘乳洞[shounyuudou] limestone cave (cavern, grotto)
洞窟[doukutsu] cave
洞穴[douketsu] cave

洞察[dousatsu] discernment
風洞[fuudou] wind tunnel
空洞化現象[kuudoukagenshou] (economic) hollowing-out phenomenon
洞見[douken] insight

雨混じりの雪[amemajirinoyuki] snow mingled with rain
花吹雪[hanafubuki] falling cherry blossoms
雪崩れる[nadareru] to slope
蛍雪の功[keisetsunokou] the fruit of diligent study
降雪[kousetsu] snowfall

豪雪[gousetsu] tremendous snowfall
細雪[sasameyuki] light snow fall
初雪[hatsuyuki] first snow (of season)
除雪[josetsu] snow removal
除雪車[josetsusha] snow-plow