This document defines and describes the key parts of a circle. A circle is defined as all points in a plane that are equidistant from a fixed center point. The main parts of a circle are the radius, diameter, circumference, chord, tangent, sector, arc, segment, and secant. The radius connects the center to any point on the circle, the diameter passes through the center and connects two points on the circumference, and the circumference is the linear distance around the entire circle. Other parts include sectors which are regions bounded by radii and an arc, segments which are portions of a circle bounded by a chord and arc, and tangents which intersect the circle at only one point.

1. Parts of a circle
radius
diameter
circumference
center
chord
sector
tangent
arc
segment
secant
point of tangency
circular segment

2. What is Circle?
Is a set of all points on a given
plane that is equidistant from a
fixed point on the plane called
the center of the circle

3. • Radius
• Diameter
• Circumference
• Tangent
• Chord
• Centre
Parts of a circle

5. • Centre – focal point of a circle
• Radius (Radii) – a segment that connects the centre and any point of the
circumference
• Diameter – a segment that connect two points of the circumference that passes
through the centre.
• Circumference – is a linear distance around a circle
• Tangent - a line that intersects a circle at one point
• Chord - a line segment whose endpoints lie on the circle
Parts of a circle

6. Other Parts of the Circle that you may be not
familiar of
• Sector (minor and major)
• Circular Segment (minor and major)
• Arc (minor and major)
• Secant
• Segment (minor and major)
• Point of tangency

7. Other parts of the circle
secant
arc
Point of
tangency
Line Segment

8. • Sector - any region in the circle bounded by two radii of a
central angle 𝜃 and the arc between their endpoints.
• Circular Segment - a portion of a circle bounded by a
chord of a circle and the arc bounded by the two endpoints of
the chord
• Arc - a portion of a circumference
• Secant - line that intersects a circle at two points
• Segment – any chord in a circle whose end points are at the
circumference
• Point of tangency - the point where a tangent line meets
the circle

9. The similarity and difference between
Circular Segment and Sector
Minor circular
segment
Major circular segment

10. Major Sector and Minor
Sector

12. Activity
• Draw a circle that is big enough, in a bond
paper or any form of paper. Label each part
with its corresponding names or term. picture
it and send or pm it to me.

13. Sector
any region in the circle bounded by two radii of a central angle 𝜃 and
endpoints.
Example:
The shaded region in the circle is a
sector.

14. Arc
a portion of the circle’s circumference.
Example:
• The curve line
connecting
points A and B
is an example
of an arc. This
is 𝐴𝐵.

15. Circular Segment
a portion of a circle bounded by a chord of a circle and the arc
endpoints of the chord
Example:
• The circular
segment is
the shaded
region
bounded by
𝐴𝐵 and 𝐴𝐵.

16. Radius
distance between the center of the circle and a point on the
circle; the plural form of radius is radii
Example:
The lines
𝑄𝐶, 𝐶𝑅,
and 𝑃𝐶
are the
radii of
circle 𝐶.

17. Chord
a line segment whose endpoints lie on the circle
Example:
The lines
𝑄𝑅, 𝑃𝑅, and
𝑄𝑃 are
chords of
circle 𝐶.

18. Diameter
a chord that passes through the center of the circle; the diameter is also
circle
Example:
The line
𝑄𝑆 is the
diameter
of circle
𝐶.

19. Secant
a line that intersects a circle in two points
Example:
The lines
𝑄𝑆 and
𝑄𝑅 are
secants
of
circle 𝐶.

20. Tangent
a line that intersects a circle at only one point; the point where it
called the point of tangency
Example:
The line 𝑈𝑉
is tangent
to circle 𝐶,
and
the point of
tangency is
point 𝑇.

21. Arc
a portion of a circle formed between two points on the circle
Example:
The arc 𝑃𝑄 is
a minor arc,
and the arc
𝑃𝑅𝑄 is a
major arc.