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.
