Students at the 3rd grade level build on their work in earlier grades where they identified and described shapes before starting to look at their attributes (e.g. number of sides). By the end of 3rd grade they should understand that shapes in different sub-categories (e.g. rhombus, rectangle) share the same attributes (e.g. 4 sides) and that shapes with these shared attributes can belong to a broader category (e.g. quadrilaterals)
Some of these terms might seem obvious to you but just assuming they are familiar to your children may lead to difficulties.
*Page, John D. "Math Open Reference" www.mathopenref.com
Discuss the above words and terms with your children. Encourage them to lead as you work through the list. The concepts of perpendicular and parallel lines and angle measurement in degrees are typically studied in 4th grade so they need not be mastered in 3rd grade although the ability to identify a right-angle is required.
A polygon is a two-dimensional shape with sides made of line segments that join at their endpoints. Your children should already have been introduced to polygons and they should be able to distinguish them from "non-polygons." Use this polygon/ non-polygon worksheet for practice with making the distinction.
Quadrilaterals are 4-sided polygons. Review the quadrilaterals shown and described below with your children. Ask them to describe them to you. Encourage them to talk about the sides, vertices, and angles and to identify the defining attributes. Good questions for you to ask include:
Check that your children can distinguish between attributes that define a category of shape (e.g. number of sides, vertices, angles, congruence) and other attributes such as size and color.
Have your children draw and categorize their own shapes using this worksheet.
The two matching games below will also help your children to practice with shape names and their defining attributes.
Help your children to identify attributes that are shared by different categories and discuss how this means a shape can belong to a larger category. For example, a square is a special type of rectangle and a rectangle is a special type of parallelogram. The diagram below illustrates the hierarchy.