AB = Diameter
Must pass through the centre of the circle. The Diameter is equal to twice the radius.
OC = Radius
The radius is a line segment that begin from the centre and touches any point on the circle.
ED = Chord
The chord joins any two points on a circle.
FG = Tangent
A line with one point common to the circle.
EHD = Arc
Only the portion of the circle that is between two points on the circle.
ADB = Semicircle
Also considered to be an arc that is exactly half of the circle.
OCB = Sector
The area between two radii and the arc.
COB = Central Angle
Fromed by two radii.
