A circle is defined as all points equidistant from a center point. The radius is the distance from the center to the circumference, while the diameter is the longest chord passing through the center. Other circle terms defined include chord, arc, segment, secant, and tangent.

2. A circle is the set of all
points in a plane that are the
same distance from a given
point, called the center of a
circle.

4. RADII IS THE
PLURAL OF RADIUS.
RADII IS THE
DISTANCE FROM THE
CENTRE TO THE
CIRCUMFERENCE.
RADII OF A CIRCLE

5. DIAMETER OF A CIRCLE
DIAMETER IS THE LONGEST
CHORD.
DIAMETER IS A STRAIGHT LINE
JOINING TWO POINTS ON A CIRCLE
AND PASSING THROUGH THE
CENTRE.

6. CHORD OF A CIRCLE
A CHORD IS A STRAIGHT LINE
JOINING TWO POINTS ON A
CIRCUMFERENCE OF A
CIRCLE.

7. An arc is the part of the
circumference.

9. A segment is the part of a
circle between a chord and
an arc.

10. A secant is a straight line
which touches a circle at two
points.

11. A tangent is a straight line which
touches a circle at only one point.
Tangent is perpendicular to the
radius through the point of
contact.