Tangent: A line that crosses the circle only once.This means that only at one point
in the line, does the line touch the circle
Sector: The space
between two radiuses.This is like degrees measured in an angle.
Secant: A line that crosses the circle only twice. This line runs right through
a circle. It is not a diameter, the length of a secant is smaller, and does not run perfectally through the
center of a circle.
Chord: A line that connects two points on the circumference of a circle. In other words
unlike a secant the chord stays within the circle, and does not go beyond the circumference.
Arc: Part of the circumference of a circle. An arc is always less than the circumference.
Circumference: The perimetre of a circle
Diameter: A line segment that passes through the centre of a circle, and reaches the edge
of the circle on the other side. Which is parellel to where the top of the line touches the circumference. Diameter
can also refer to the length of this line, which runs the 2 parellel points.