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Teachers & SchoolsStudy Guide

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.**Radius:**the distance from the center of a circle to a point on the circle.**Diameter:**the distance across a circle, through the center of a circle. The diameter can be made by putting two radii together, end to end. The diameter is equal to two times the radius, or*d*= 2*r*.**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.