A diagonal from a polygon is a line segment that joins two nonconsecutive points.
A line segment that intersects with or joins two points on a circle is called a chord.
A chord is a line that joins to points on the circumference of a circle. If it passes through the center of the circle it's called a diameter.
This is a diagonal line. The definition of a diagonal is a line that joins two nonconsecutive vertices or corners of a polygon.
That's the diameter.
A line segment in a polygon connecting any two nonconsecutive vertices is called a diagonal.
diameter
a line that joins two points on a circle
A contour is a line that joins points of equal elevation.
A line is a straight path that extends infinitely or endlessly in opposite directions. A straight path that joins two points is called a line segment.
That may mean the line segment that joins points labelled Q and Z.
Points on the same line are called collinear points.