A point is a location on anything.

A line is a path that goes on forever!

A part of a line that does not go on.

Two rays that are sharing an endpoint.

A part of a line that has one endpoint. It goes on in one direction.

An an angle that is more than ninety degrees.

This an angle that is ninety degrees.

An acute angle is less than ninety degrees.

They're lines that will never touch.

These are lines that cross each other.

They're intersecting lines that form four right angles.

This is the middle of the circle.

Chords (pronounced like "cord") are line segments that end on the boundaries of a circle.

Diameters are chords that cross the middle of the circle.

They're half a diameter.

(Ellen April 24, 2008)