$\Theta \rho ϵ\eta \Pi \alpha \tau \pi$

Suppose that $G$ is a group and that $\varnothing \subset H\subseteq G$, then we define $$aH:=\{ah:h\in H\}$$

Suppose that $G$ is a group and that $\varnothing \subset H\subseteq G$, then we define $$Ha:=\{ha:h\in H\}$$