2D Shapes
Lessons in this chapter
About 2D Shapes
This is the chapter where shapes stop being pictures and start being categories: a triangle is anything with three straight sides, whatever size it is and whichever way it is turned.
It opens with Identify Straight and Curved Lines, because every 2D shape a kindergartener meets is built out of one or the other. A child who can see that a circle has no straight sides has already got the tool for telling circles from squares without memorizing either.
Identify Triangles, Identify Rectangles and Identify Squares then work through the straight-sided shapes one at a time. The hard part is not naming a textbook triangle sitting flat on the page; it is recognizing a thin, tilted one as the same shape. The lessons keep varying size and orientation for exactly that reason.
Identify Circles and Semicircles brings in the curved shapes, and Identify More New Shapes adds the ones kids meet in the world, so the chapter ends with a child who can look at a sign, a window or a slice of toast and name what shape it is.
Each of the six lessons comes with its own worksheet, worked in the page and scored as you go. Identify Straight and Curved Lines, Identify Triangles and Identify Circles and Semicircles ask a child to pick the shape out of a mixed set rather than copy a drawing of it, which is the part that makes the naming stick. All six are free to practice online.
Frequently asked questions
Six lessons. It opens with Identify Straight and Curved Lines, because every shape that follows is described by which kind of line it is made from, then works through triangles, rectangles, squares, and circles and semicircles, and ends with Identify More New Shapes. These 2D shapes sit in the Common Core kindergarten Geometry domain (K.G).
Triangle, rectangle, square, circle and semicircle, plus the ability to tell straight lines from curved ones. Identify More New Shapes adds a few beyond that set for kids who are ready.
Because it makes every other lesson easier. Once a child knows a shape is made of straight sides or curved ones, telling a circle from a square stops being memory and starts being a check they can run themselves.
Turn it back. Rotating the shape in front of them and asking whether anything about it changed is usually enough. A square is still a square at any angle, and the lessons keep showing shapes rotated so this does not harden into a habit.
Every square is a rectangle, because it has four straight sides and four square corners. What makes it a square is that all four sides are the same length. Kindergarteners are not expected to state it that formally, only to sort the two reliably.
Half a circle: one curved edge and one straight edge. It is worth knowing at this age mainly because it shows kids that a shape can mix straight and curved sides, which breaks the assumption that shapes are either one or the other.