Let XX be a over K=R\mathbb K=\mathbb R or C\mathbb C, and let f:XKf:X\to\mathbb K be a nonzero linear functional. Then its has codimension one:

codim(kerf)=1.\operatorname{codim}(\ker f)=1.
Remarks

The kernel of a nonzero functional is a codimension-one subspace, and translates of such kernels are precisely in real vector spaces; see .