九牛一毛的英文：
[Literal Meaning]
nine/ox/one/hair
a single hair out of nine ox hides

[解释]
九头牛身上的一根毛。比喻极大数量中极微小的数量，不值得考虑。

[Explanation]
comparatively tiny and insignificant

[例子]
这点钱对他来说就是九牛一毛，你不用太担心。

[Example]
This little amount of money is a drop in the ocean to him, and you need not worry.

[英文等价词]
a drop in the ocean

For him the loss was only a drop in the ocean.
这点损失对他来说,只不过是九牛一毛。