Triangles
There is no special name: they are polygons, as are shapes with 3 or 3 million sides.
Polygons are shapes with 3 or more sides
Triangles have 3 sides.
A triangle
A Triangle
It is a polygon that has 3 or more sides
Triangles
a triangle
A triangle.
An equilateral triangle.
They are polyhedra.
Angle