Concentric Circles
From Latin: com "together" + centrum "center."
Definition: Circles that have their centers at the same point
Try this Drag either orange dot to resize the circles. Note how they always retain the same centers.

Concentric circles are simply circles that all have the same center. They fit inside each other and are the same distance apart all the way around. In the figure above, resize either circle by dragging an orange dot and see that they both always have a common center point.

Other circle topics

General

Equations of a circle

Angles in a circle

Arcs