Fundamental group of a once-punctured torus
= Fundamental group of a once-punctured torus
{title2=$\pi_1(T^2\setminus B^2)\cong F_2$}
Removing an embedded <open disk> from the <torus> leaves a <topological surface> with one boundary <circle>. In the square model, radial expansion away from the removed <disk> gives a <deformation retraction> onto the square boundary with opposite sides identified, a <wedge of two circles>. Its <fundamental group> is therefore the <free group> on two <group generators>.