There's the concept of "expected value of the next reward", often denoted as $\mathcal{R}^a_{ss'}$, and defined as $$ \mathcal{R}^a_{ss'} = \mathbb{E}\left(r_{t+1} \mid s_t = s, a_t = a, s_{t+1} = s' \right) $$ which is the value we expect for the reward at the next time step, that is at time ...