A 5-sided 2D shape would be a pentagon, pent, meaning 5.
10 sided 2D shape is called a decagon 20 sided 2D shape is called a icosagon 30 sided 2D shape is a swimming pool 40 sided 2D shape is unknown 50 sided 2D shape is unknown 60 sided 2d shape is unknown 70 sided 2d shape is unknown 80 sided 2d shape is unknown 90 sided 2d shape is unknown 100 sided 2d shape is unknown 110 sided 2d shape is unknown 111 sided 2d shape is unknown 120 sided 2d shape is unknown 130 sided 2d shape is unknown
A pentagon
A seven sided 2D shape is a heptagon.
A 5 sided pentagon fits the description
A 2d nine sided shape is called a nonagon.
As a 2D polygon shape it is an 8 sided octagon.
a triangle
Any 4 sided 2D shape
Such a 2D shape is a hexagon, a six sided figure.
A 2D shape with forty sides is known as a tentracontagon.
triskaidecagon
Tetrahaidecahedron