Mathematics
Linear Independence and Spanning Sets in Vector Spaces
Quick fact
The smallest number of vectors needed to span a space is called its dimension—for example, you need exactly two independent vectors to cover a plane, and three to cover our familiar 3D space. Adding more vectors beyond that will either be redundant or force the space to become infinite-dimensional.
Why this is interesting
Imagine you have a set of arrows. Can you always reach every point in space by scaling and adding them together? And do you ever have more arrows than you actually need?