\overparen - Used to put a (stretchy) over-parenthesis (over-arc, frown) over the argument.
{ \overparen #1}
\overparen command puts a (stretchy) over-parenthesis (over-arc, frown) over the argument.
\overparen a \quad \overparen ab \quad \overparen{ab} \quad \overparen{abc} \quad \overparen{abcdef} \quad \overparen{\underparen{abcd}}