$$\newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} }$$
$$\newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}}$$
Thumbnail: Angle $$θ$$ and intercepted arc $$\overparen{AB}$$ on circle of circumference $$C = 2πr$$.