Using "$\cdot$" as variable placeholder – math.stackexchange.com

Using "$\cdot$" as variable placeholder – math.stackexchange.com

I've occasionally come across the use of "$\cdot$" as placeholder for a
variable, most recently in a paper on radial basis functions, which were
defined as $$ s(\cdot) = p(\cdot) + \sum_{i=1}^N ...