> [!NOTE] Definiton > Let $V$ be a [[Vector Space|vector space]]. Let $W_{1},W_{2}\subset V$ be [[Vector Subspace|subspaces]] of $V.$ Then we define their **sum** to be the [[Span of Subset of Vector Space|span]] of their [[Set Union|union]] $W_{1}+W_{2}=\langle W_{1} \cup W_{2} \rangle$ # Properties