The arithmetic law of vectors defines the meaning of multiplying a number by a vector, and also defines that the two must be equal. This is artificially defined, and it is meaningless for you to delve into it, just as you ask why apples are called apples instead of bananas.

Vector (English: vector, physics, engineering, etc. ) is a basic concept in mathematics, physics, engineering science and many other natural sciences. Refers to a geometric object that has both size and direction and satisfies the parallelogram law. Vector notation: print letters (such as A, B, U, V) in bold, and add a small arrow "→" at the top of the letter when writing. If the starting point (a) and the ending point (b) of the vector are given, the vector can be recorded as AB (and added to the top →). In the spatial cartesian coordinate system, vectors can also be expressed in pairs. For example, (2,3) in the Oxy plane is a vector. In physics and engineering, geometric vectors are more often called vectors.