Vector space dimension

Set

 context $V$…$\ \mathcal F$-vector space
 definiendum $\mathrm{dim}(V)\equiv \mathrm{card}(B)$
 context $B\in\mathrm{basis}(V)$

Discussion

For finite vector spaces, the basis cardinality $\mathrm{dim}(V)$ is the only invariant w.r.t. vector space isomorphisms.

The Zero vector space has an empty base. Its vector space dimension is zero.

Reference

Wikipedia: Vector space