you begin the second one.

再画第二个矢量
The sum starts at the beginning of the first

和矢量就是从第一个矢量的起点
and ends at the end of the second.

指向第二个矢量的终点
Okay, so that tells you how to add two vectors and get a sum.

这就是矢量的加法法则
You can verify, in this simple example,

在这个例子中还可以验证
B + A would be--First draw B and from there you draw A.

B + A 就是先画矢量 B 然后再画矢量 A
You will end up with the same point.

最终你还是得到同一个终点
You say this is a commutative law.

这就是交换律
It doesn't matter the sequence in which you add the two vectors.

在做两个矢量的加法时无所谓相加的顺序
You know that's true for ordinary numbers, right?

这对于普通数字的加法成立不是吗
3 + 4 and 4 + 3 are the same.

3 + 4 和 4 + 3 结果一样
It's also true for vectors.

它对矢量同样也成立