Which Greek letter is commonly used to represent a count? For example, the Greek letter sigma ($\Sigma$) is commonly used to represent a sum.
$\endgroup$ 41 Answer
$\begingroup$While your "count" is quite vague, here is a possibility:
The count of elements in a set:
What symbol gives the count of elements in a set?
The latin letter N is, as pointed out in the comments, also sometimes used.
$\endgroup$