# What is the y intercept for a line with point (0,6) slope is undefined?

The "y-intercept" is the whole of the $y$ axis, i.e. the line $x = 0$.
An undefined slope means a vertical line. The equation of the vertical line passing through $\left(0 , 6\right)$ is $x = 0$.
The $y$ axis has the equation $x = 0$ too, so the line and the axis intercept at all points of the $y$ axis.