A proton contains two “up” quarks and one “down” quark.

质子包含两个“上” 夸克和一个“下” 夸克。

A proton is made of two up quarks and one down quark, and a neutron is two down quarks and an up quark.

质子由两个上夸克和一个下夸克组成，中子由两个下夸克和一个上夸克组成。

But the important thing here is that the up and down quarks are much lighter than the other four, like charm and strange.

但这里重要的是，上下夸克比其他四个要轻很多，喜欢魅惑和奇异。