I have always taught my students that the $y$-intercept of a line is the $y$-coordinate of the point of intersection of a line with the $y$-axis, that is, for the line given by the equation $y=mx+y_0$, the $y$-intercept is $y_0$. I emphasize that that the $y$-intercept is the number $y_0$ and not the point $(0,y_0)$.
But I was quite surprised when I recently looked at the Wikipedia and Wolfram MathWorld entries for $y$-intercept because these define the intercept as a point and not as a number ("the point where a line crosses the y-axis" and "The point at which a curve or function crosses the y-axis").
Further investigation yielded inconsistencies: the Wikipedia entry for "Line (geometry)" states that in the equation $y=mx+b$, "$b$ is the y-intercept of the line"; the Wolfram MathWorld entry for "Line" states that "The line with $y$-intercept $b$ and slope $m$ is given by the slope-intercept form $y=mx+b$.
Is there a trusted source targeted at mathematics educators (from, say, a government agency, an educational institution, or an organization) that defines "intercept" and consistently uses that definition?