Circle : A circle is a two-dimensional shape. The boundary of a circle is a set of points that has the same distance (the radius) from the center of the circle.

Line segment : A line segment AB is a one-dimensional shape consisting of the points A and B and all the points on the straight connection of A and B. A and B are both endpoints of the line segment AB.

Pyramid : A pyramid is a polyhedron that has a base equal to a polygon. In addition to the corners in the polygon the pyramid has exactly one additional corner, the so called apex of the pyramid. All the corners of the base shape are connected to the apex and all the faces besides the base face are triangles.

Quadrilateral : A quadrilateral or quadrangle is a polygon with four corners. Rectangles, trapezoids, kites, rhombuses, squares and parallelograms are all specific kinds of quadrilaterals. The sum of the interior angles in a quadrilateral is always $360^{\circ}.$

Shape : A shape is a set of points in space.

Three-dimensional shape : A three-dimensional shape is a shape that has a volume.

Volume : Volume refers to the size of a three-dimensional objects measured by how many unit cubes it would take to fill the shape.

Count : To count means to find out the number of objects by adding one for every object.

Number : A number $x$ is a mathematical symbol representing a quantity.

Count : To count means to find out the number of objects by adding one for every object.

Number : A number $x$ is a mathematical symbol representing a quantity.