V is finite if every linearly independent set is finite.
ie, if for every set E⊆V such that ∀v1,…,vN∈E∑i=1Naivi=0⟹a1=⋯=aN=0
and E has finite cardinality, then V is finite-dimensional. Otherwise, V is infinite-dimensional.
Example
C([0,1]) is infinite dimensional because
E={fn(x)=xn∣n∈N∪{0}}
is a linearly independent set with non-finite cardinality.