TRIANGLE
A triangle is a closed flat shape, or polygon, with 3 sides and three angles. There are three types of triangles: equilateral, isosceles, and scalene. The one in this picture is an example of an isosceles triangle. Two of its sides (line segments) measure the same length. The third side (the base) measures a different length. Because an isosceles triangle has two sides that are the same and that meet at a midpoint above/next to the base, only two angles actually measure the same degree. The third depends on how wide the base is.