a triangle
A shape with straight sides is called a polygon. But it can have 3 or 4 sides as well.
polygon
A shape with 7 sides is a heptagon
You could call it a regular hexagon, especially if it is one.
you call a two dimensional shape with six sides a hexagon
When two sides (called faces) of a 3-dimensional shape meet, they meet at an edge.
Triangle is a shape with three sides.
A shape with 8 sides is an octagon.
A regular shape.
a shape with nine sides is called nonagon
It is an irregular shape