4
There is no specific name - other than what you used: "a pair of parallel line segments".
Three pairs. The line joining the midpoints of any two sides of a triangle is always parallel to the third side of the triangle (and half its length).
A circle.
They are equal line segments that meet at an angle of 135°.
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how many pairs of parallel line segments does a stop sigh have
NoneOctagon hasn't got any pairs of parallel line
rectangle, octagon, hexagon
Pair of radii
A quadrilateral with 2 pairs of parallel line segments is a parallelogram. Parallelograms include rectangles, rhombuses, and squares.
A regular hexagon has three sets (pairs) of parallel line segments that form it.
Many polygons, such as squares, rectangles, rhombi, parallelograms, etc. have more than 1 pairs of parallel line segments. Trapezoids have only 1 pair of parallel line segments. These few shapes are just quadrilaterals, other polygons also have more than 1 pair of parallel line segments (e.g. regularhexagons, octagons, etc.). Triangles never have any parallel line segments.
No
A square has two sets of parallel line segments. "Parallel" does not describe a square, however.
They can not be line segments on the same line, but they can both be line segments.
An 8 sided octagon has 8 line segments which are its 8 sides
8 of them because an octagon is an 8 sided polygon