up to four pairs is the answer
On a quick estimate, I would think 18, 9 for each interior side and another 9 for each interior angle. * * * * * A nonagon has only 9 lines so the above answer is nonsense. With 9 lines you can have at most 4 pairs of parallel lines (and one not parallel to any). Or you could have a concave nonagon with 1 pair, 1 triplet and 1 quartet of parallel lines, or some other combination.
A pentagon has no parallel lines.
Here are three shapes that have two pairs of parallel lines: square parallelogram rectangle There are many polygons with at least two pairs of parallel lines. hexagon (has 3 pairs of parallel lines) octagon (has 4 pairs) decagon (has 5 pairs)
0 pairs
A regular pentagon has no parallel lines.
In a regular nonagon no two sides are parallel.
Up to four.
On a quick estimate, I would think 18, 9 for each interior side and another 9 for each interior angle. * * * * * A nonagon has only 9 lines so the above answer is nonsense. With 9 lines you can have at most 4 pairs of parallel lines (and one not parallel to any). Or you could have a concave nonagon with 1 pair, 1 triplet and 1 quartet of parallel lines, or some other combination.
A diamond has two pairs of parallel lines.
A rhombus has 2 pairs of parallel lines.
it has 2 pairs of parallel lines
A regular dodecagon has six pairs of parallel lines.
A nonagon can have none, or anything up to four pairs of parallel sides. You can even have two quartets of parallel sides in you allow concave nonagons.
it has too parallel lines!
A pentagon has no parallel lines.
A regular octagon has four pairs of parallel lines.
A square has 2 pairs of equal opposite parallel lines