Definition
Cylinder
A right circular cylinder has two congruent parallel circular bases joined by one curved surface.
Continue from this idea into connected AXIO math.
What it means
Imagine stacking identical circular cards straight upward. The first and last circles are the bases, and the outside edge of the stack makes one curved side. The circle never changes size from bottom to top.
Remember it
Same circle, straight stack.
Example
A solid has circular bases of radius 2 cm in parallel planes 5 cm apart. A slice parallel to either base is always a circle of radius 2 cm, so the solid is a right circular cylinder.
Watch for
A dented can is only approximately cylindrical because its parallel cross-sections are no longer all the same circle.
Common mix-up
A prism has polygonal bases and flat side faces; a cylinder has circular bases and one curved side surface.
Exact meaning
On this page, cylinder means a right circular cylinder: a solid with two congruent, parallel circular bases whose centres are joined by a segment perpendicular to both base planes. Every cross-section parallel to a base is the same circle.