What are Y and y in a probability density function f_Y(y)?

[nhrock3]

$$f_Y(y)$$

f means density function what are Y and y
?

 

[Synaesthesia]

It's probably the partial derivative of f with respect to Y at y.

 

[radou]

Or, in some cases, the capital Y can represent the restriction of the domain of f to Y.

 

[nhrock3]

with respect to probability(its not what you said)

 

[HallsofIvy]

$f_Y$ is the given density function of random variable Y and $f_Y(y)$ is its value for some specific value y.