Objectives
 Define the three dimensions of length, width, and height.
 Define and identify collinear points and coplanar points and lines.
 Identify objects that are zero, one, two, and threedimensional.
 Relate the concept of infinity to one, two, and threedimensional objects.
Key Terms
 Infinite – having no boundary or limit.
 Collinear – lying in a straight line. Three or more points are collinear if a straight line can be drawn through all of them.
 Plane – a flat surface that extends forever in all directions (infinite). A plane has no thickness, so it has only two dimensions (length and width).
 Coplanar – lying in the same plane. Four or more points are coplanar if there is a plane that contains all of them.
 ZeroDimensional – having no length, width, or height (ex. points)
 OneDimensional – having length but no width or height (ex. lines, line segments, rays)
 onedimensional with infinite length: lines and rays
 onedimensional with measurable length: line segments
 TwoDimensional – having length and width but no height (ex. planes / flat surfaces you can’t pick up)
 ThreeDimensional – having length, width, and height (ex. solids, geometric space, our world, things you can grab and hold)
Notes
Dimensions 

Collinear 

Coplanar 
