Let $\Sigma_g$ be a Riemann surface of genus g, and $C$ is a cut curve of $\Sigma_g$, i.e. an oriented simple close curve.
What is a righthanded Dehn twist of $C$ of $\Sigma_g$?
Let $\Sigma_g$ be a Riemann surface of genus g, and $C$ is a cut curve of $\Sigma_g$, i.e. an oriented simple close curve. What is a righthanded Dehn twist of $C$ of $\Sigma_g$? 


Cut the curve with a scalpel, going along the curve (it is oriented), rotate the right side 360 degrees, and glue it back in... 

