Definition (DMS)

A discrete memoryless source (DMS) is an infinite sequence of independent and identically distributed (iid) RVs $\{X_i\}_{i=1}^\infty=\{X_1,X_2,\cdots\}$. In particular, all RVs $X_i$ have a common pmf $p_X$ defined on $\mathcal{X}$ (finite set).