This is a diagonal line that appears to converge in linear perspective.

horizontal line
vanishing line
orthogonal line
vertical line

Question

This is a diagonal line that appears to converge in linear perspective.  

horizontal line
vanishing line
orthogonal line
vertical line

anonymous · Answer

I guess it has to be an horizontal line

anonymous · Answer

This looks like a vanishing point description, the one used in Arts, but I guess it's not this here :-(

anonymous · Answer

I think it is similar to that but in perspective drawing.....

anonymous · Answer

Hmm, but in linear perspective, you draw with 2-3 (IIRC) vanishing points. Maybe a line joining two vanishing points is a vanishing line? Never heard of that name.

anonymous · Answer

Well, me either, mainly  I just don't think it is any of the other three:-)

anonymous · Answer

Well, then I guess you are correct, it should be a horizontal line, thinking about the railroads on a plane.

anonymous · Answer

Yes....or a checkerboard.