It goes back in time when wealthy people had butlers, and maids to
help them to dress: men normally dressed themselves but ladies
had other women to help them dress and women naturally had
clothing buttons reversed to help maids clothe them. And, the tradition
continues to this day with the reversed buttons on women's clothing.
Some think it is because women used to be dressed by others therefore the sides were reversed.
paramid
They are the sides facing each other at opposite sides.
rectangle
Opposite sides are parallel.Opposite sides are congruent.Opposite angles are congruent.
The opposite sides of a parallelogram are parallel
A heptagon has seven sides so there are no pairs of opposite sides.
Parallelogram opposite sides are congruent opposite sides parallel
parellelagram
A parallelogram has opposite equal parallel sides
a decagon i believe has either 5 or 20 opposite sides * * * * * A decagon has 10 sides so I cannot see how it could have 20 opposite sides. It has 5 pairs of opposite sides but this does not mean that these opposite sides face each other. In an irregular decagon it is quite possible for opposite sides to be at right angles or at any angle to each other.
The description given fits that of a square or a rhombus