Conditional density
= Conditional density
{title2=$f_{Y\mid X=x}(y)$}
= Conditional probability density
{synonym}
Where the <marginal density> $f_X(x)$ is positive, a <joint probability density> determines the conditional density
$$
f_{Y\mid X=x}(y)=\frac{f_{X,Y}(x,y)}{f_X(x)}.
$$
It integrates to one in $y$, and supplies <conditional expectations> by integrating against it. Its values on a probability-zero set of conditioning points are not fixed by the <joint probability distribution>.