# Circles

## Parts of a circle

You will need to make sure you can identify all aspects of a circle.

Let’s start with some key lines that make elements of a circle.

The **radius** is always half the diameter.

The **diameter** goes across the circle, through the middle of the circle.

A **chord** it is a line that touches the circumference at two points but does not cross the middle of the circle.

A __tangent __ to the circle touches the circle at only one point.

The __circumference __of the circle (it’s like the perimeter of the circle).

A **secant** is a line that intersects the **circle** in two different points.

An **arc** this is part of the circumference.

A **sector** it is part of the circle enclosed by two radius or by two points on the circumference.

An area not enclosed by two radii is called a **segment**.

- What is the name for the area of a circle between the circumference and two radii?
- Sector
- What is half the diameter?
- Radius
- What touches a circle at one point?
- Tangent