The strongest shape is a triangle, which can be utilized in many applications by combining a series of triangles together. Triangles are frequently used in construction of bridges and buildings due to their strength.
The primary reason for a triangle's strength is its rigid composition. When force is applied to a triangle, most of the stress is transferred to the vertices because the internal angles and sides are fixed. A triangle will not deform; it will either withstand the stress or break. In comparison, when force is applied to a square, specifically on one of the sides, it can buckle in and cause the shape to collapse.