Vectors can be used to represent physical entities such as forces, and they can be added to each other and multiplied with scalars, thus forming the first example of a real vector space.

• 在这里，一个向量是一个有方向的线段，由长度和方向同时表示。这样向量可以用来表示物理量，比如力，也可以和标量做加法和乘法。