by Seth Grief-Albert
The set of all linear combinations.
3Blue1Brown
$$ c_1v_1+c_2v_2+c_3v_3 $$
A span is a vector subspace. Vector subspaces are closed under vector addition and scalar multiplication.
Vector subspaces are closed under vector addition and scalar multiplication.
Any linear combination of elements in a vector space V will also be in the vector space.
Redundancy
Non-zero scalar multiples of the vectors produce the zero-vector.
Although parallel vectors are dependent in R2, not all dependent vectors are parallel.