There are a number of functions in mathematics denoted with upper or lower case s.
1. The nome .
2. A prefix denoting q-analogs and q-series.
3. or with , 1, 2, 3 denote the q-products.
4. The normal distribution function is sometimes denoted .
5. denotes the Marcum Q-function.
6. is used to denote the partition function Q.