雲泥(うんでい)の差(さ)

An idiomatic expression combining 雲(うん) (clouds) and 泥(でい) (mud) — the most distant extremes — with 差(さ) (difference). The image is that two things are as far apart as the sky and the ground.

Etymology

From classical Chinese, comparing the distance between clouds (the highest) and mud (the lowest). The standalone compound 雲泥(うんでい) already means "vast difference," and adding の差(さ) makes this explicit.

Usage

Almost always used in the pattern ～には雲泥(うんでい)の差(さ)がある (there is a world of difference in ~). Can describe positive or negative comparisons.

Similar words

• 天(てん)と地(ち)ほどの差(さ) — difference as great as heaven and earth (similar meaning)
• 月(つき)とすっぽん — comparing the moon and a snapping turtle (two things that look similar but are vastly different in quality)
• 大(おお)きな差(さ) — big difference (plain, non-idiomatic)