For an iid sequence (x₁, x₂, …, x_n) ∊ {0,1}ⁿ one would expect for a typical sequence that

where H(X) denotes the Shannon entropy of the distribution. For ε‎ > 0, the typical set $T_n^{\epsilon }$ is the set of sequences (x₁, x₂, …, x_n) such that

It is then probable that a sequence will arise from the typical set despite, in most cases, $T_n^{\epsilon }$ being much smaller than 2ⁿ in size.