Under vectors in LaTeX

Symbol Command
$\underrightarrow{AB}$ \underrightarrow{AB}
$\underbar{AB}$ \underbar{AB}
$\underline{AB}$ \underline{AB}
$\underlinesegment{AB}$ \underlinesegment{AB}
$\undergroup{AB}$ \undergroup{AB}

LaTeX vector

LaTeX