great difference; worlds apart
Used in the set phrase 雲泥の差 (うんでいのさ) to describe a vast, almost incomparable difference, like that between clouds and mud. Rarely used outside this phrase.
There is a world of difference in their abilities.
From Chinese 雲泥 (yúnní), literally 'clouds and mud', used figuratively for a vast difference. The Japanese usage is almost entirely limited to the set phrase 雲泥の差.