This document defines and illustrates key terms related to circles: a circle consists of points equidistant from a center point; the radius connects the center to the edge; the circumference is the distance around the circle; congruent and concentric circles share radii lengths or centers, respectively; a chord connects two edge points; the diameter passes through the center; an arc is part of the edge between two points; and a sector is the region between two radii and their connecting arc.

2. • Circle
• Radius
• Circumference
• Congruent Circle
• Concentric Circle
• Chord
• Diameter
• Arc
• Sector

3. CIRCLE
A circle may be defined as the collection of
points which are at equal distance from a fixed point.
.c

4. RADIUS
A segment from a point on the circle to
the center of the circle.
Radius
C.

5. CIRCUMFERENCE
The circumference is the distance around
the circle.
circumference
C.

6. CONGRUET CIRCLE
Two circles whose radii have the same
measure.
C.C.

7. CONCENTRIC CIRCLE
Two or more circle that share the same
center.
.C

8. CHORD
A chord of a circle is a segment whose
endpoints lie on the circle.
A B
C
D
D
.O

9. DIAMETER
A chord passing through the center of a
circle.
A Q BC.

10. ARC
An arc is part of a circle connecting
two points of the circle.
A P
Arc
B Qc.

11. SECTOR
A sector is a region contained by two
radii and an arc.
A
Sector
B
CCC Q
C.

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