Bisection along a line of symmetry.
A dodecagon or dudecagon are both acceptable terms
A shape with 7 sides is a heptagon
you call a two dimensional shape with six sides a hexagon
A shape with 8 sides is an octagon.
Triangle is a shape with three sides.
A shape with five sides would be a pentagon, but a shape can not have 5 right angles. Squares and Rectangles are both shapes with 4 sides and 4 right angles. They are the only shape with the same amount of right angles as there is sides.
A regular shape.
It is an irregular shape
a shape with nine sides is called nonagon
A shape with straight sides is called a polygon. But it can have 3 or 4 sides as well.
A shape with 5 sides is a pentagon
A TRIGON , more usually a 'Triangle'.