Closed surface
= Closed surface
{title2=$S_g$}
A <compact> two-dimensional <manifold> without boundary. A <connected> <oriented surface> is classified by its <genus>; for <genus> $g$ its <Euler characteristic> is $2-2g$.
= Closed surface
{title2=$S_g$}
A <compact> two-dimensional <manifold> without boundary. A <connected> <oriented surface> is classified by its <genus>; for <genus> $g$ its <Euler characteristic> is $2-2g$.