A circle is the set of all points equal in distance from a center point. If you pinned a piece of yarn down, then tied a pencil to the other end of the yarn and pulled the pencil around, you'd roughly draw a circle.
Here are some more definitions that you need to know
- Chord: a line segment connecting two points on a circle.
- Diameter: the distance across the center of a circle.
- Radius: the distance from the center of a circle to a point on the circle.
- Secant: a line intersecting a circle at two points.
- Tangent: a line intersecting a circle at exactly one point.
All circles are similar, meaning that they have the same shape but may be different sizes.