In 2D figures, identify sides having the same length, which shape has fewer or more sides, which shape has fewer or more corners (more formally, vertices), and which shape is round. In 3D figures, identify which has fewer or more corners, and which has fewer or more faces.

Understanding Common Core Math (Standard K.G.B.4) by Understanding Common Core Math

Compare shapes by Khan Academy

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K.G.B.4: Analyze and compare two- and three-dimensional shapes, in different sizes and orientations, using informal language to describe their similarities, differences, parts (e.g., number of sides and vertices/"corners") and other attributes (e.g., having sides of equal length).