Meaning of symbol used for vector spaces

Question

I found this problem:

Let V be an F-vector space of finite dimension, and let S and T be subspaces of V. Prove that $$ (S+T)^{o}=S^{o} \cap T^{o} $$

Question:

What's the meaning of the small circle when used as an "exponent" of a vector space?

Answer 1

Most probably, the exponent is a zero, and $S^0$ is the annihilator of $S$, that is, the set of linear functionals $f \in V^*$ such that $f(s)= 0$ for all $s \in S$.