typical sequence
where H(X) denotes the Shannon entropy of the distribution. For ε > 0, the typical set 
is the set of sequences (x1, x2, …, xn) such that
It is then probable that a sequence will arise from the typical set despite, in most cases, 
being much smaller than 2n in size.
- subgraph
- subgroup
- subgroup generated by a set
- subject
- submatrix
- subring
- subscript
- subsequence
- subset
- subspace
- subspace topology
- substitution
- substitution group
- subtend
- subtraction
- sufficient condition
- sufficient estimator
- sufficiently large
- sufficient statistic
- sum
- summation notation
- sum to infinity
- sup
- superadditive
- superposition principle