# What is a cylinder?

Everyone taught geometric figures in school, one of which is a cylinder. About what the cylinder is, our article will tell.

A cylinder (circular cylinder) is a body that consists of:

- from two circles that are combined in parallel transfer
- segments that connect the corresponding points of these circles

What is the base of the cylinder? The bases of the cylinder (two of them) are the above-mentioned circles, and the segments, which are also mentioned above, are the generators of this cylinder.

The bases of the cylinder lie in parallelplanes and are equal to each other, and the generators are equal and parallel to each other. The surface of such a cylinder consists of a lateral surface and bases. The very same side surface is composed of generatrixes.

A cylinder (a straight cylinder) is a cylinder in which all the generators are perpendicular to the planes of its base.

The cylinder can be imagined as a body, which is obtained by rotating a simple rectangle around an axis (one side).

There are also other types of cylinders:

- elliptical
- parabolic
- hyperbolic

Prism is also considered as the kind of cylinder.

## Necessary Notions

- The height of any cylinder is the distance between the planes in which the bases lie.
- The radius of any cylinder is the radius of its base.
- The cylinder axis is a straight line that passes through both centers of the cylinder bases. It is parallel to generators.
- A plane that passes through anyforming a straight cylinder and at the same time perpendicular to the axial section, which is drawn through the same generatrix, is called the tangential plane of the straight cylinder.
- The cross-section of any cylinder by a plane that passes through its axis is called the axial section.
- A plane that is perpendicular to the axis of the cylinder will intersect the lateral surface of the cylinder along a circle that is equal to the circumference of the base.