If a straight line is not running horizontal or vertical, what orientation is it likely to have?

The most appropriate orientation for a straight line that is not running horizontal or vertical is inclined. An inclined line is one that slants or is tilted at an angle, which effectively captures the idea of a straight line positioned between horizontal and vertical orientations.

While the term diagonal might seem relevant, it commonly refers to lines that bisect angles or connect opposite corners in a geometric context, such as in squares or rectangles, rather than simply indicating a slant. Curved suggests a bend or change in direction, which does not apply to straight lines at all. The term perpendicular describes a relationship between two lines that meet at right angles, which is not applicable when discussing a single line that is not horizontal or vertical. Therefore, inclined is the most accurate term to describe the orientation of the straight line in this scenario.