Circle Vocabulary Worksheet

Press Print worksheet to match twelve parts of a circle, from radius to sector, to their meanings.

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NameDateMade at homeroomtools.comDraw a line from each one on the left to its partner on the right.Circle vocabularycirclecenterradiusdiameterchordcircumferencearcsemicirclesectorsegmentpidiskthe point equally far from everypoint of the circlethe longest chord, twice theradius in lengththe region between a chord andthe arc it cuts offa segment that joins the center tothe circlethe ratio of circumference todiameter, about 3.14a wedge of the circle with its tipat the centerthe length of the circle's fullcurveevery point in a plane at one fixeddistance from a centeran unbroken piece of the circle'scurvea segment whose two endpointslie on the circlea circle together with all thepoints inside itthe half-circle on either side of adiameter
NameDateMade at homeroomtools.comDraw a line from each one on the left to its partner on the right.Circle vocabularyAnswer keycirclecenterradiusdiameterchordcircumferencearcsemicirclesectorsegmentpidiskthe point equally far from everypoint of the circlethe longest chord, twice theradius in lengththe region between a chord andthe arc it cuts offa segment that joins the center tothe circlethe ratio of circumference todiameter, about 3.14a wedge of the circle with its tipat the centerthe length of the circle's fullcurveevery point in a plane at one fixeddistance from a centeran unbroken piece of the circle'scurvea segment whose two endpointslie on the circlea circle together with all thepoints inside itthe half-circle on either side of adiameter
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All 36 terms

Parts of a circle 12

  • arc An unbroken piece of the circle's curve. Two points on a circle split it into two arcs.
  • center The point equally far from every point of the circle. A circle is named by its center: circle O.
  • chord A segment whose two endpoints lie on the circle. A chord need not pass through the center.
  • circle Every point in a plane at one fixed distance from a center. A coin's rim has the shape of a circle.
  • circumference The length of the circle's full curve. C = 2πr.
  • diameter The longest chord, twice the radius in length. If the radius is 4, the diameter is 8.
  • disk A circle together with all the points inside it. A circle is only the rim; a disk is filled in.
  • pi The ratio of circumference to diameter, about 3.14. The symbol is π.
  • radius A segment that joins the center to the circle. Every radius of one circle has the same length.
  • sector A wedge of the circle with its tip at the center. A slice of pizza has the shape of a sector.
  • segment The region between a chord and the arc it cuts off. A chord splits the inside of a circle into two segments.
  • semicircle The half-circle on either side of a diameter. A semicircle measures 180°.
Show all 36 terms (24 more)

Lines, angles and arcs 12

  • central angle An angle formed by two radii. A central angle has the same measure as its arc.
  • concentric circles Circles that share a center but differ in radius. The rings of a target are concentric circles.
  • concyclic Lying on one and the same circle. The four corners of a rectangle are concyclic points.
  • inscribed angle An angle formed by two chords that meet on the circle. It measures half of its intercepted arc.
  • major arc An arc longer than half the circle. A major arc measures more than 180°.
  • minor arc An arc shorter than half the circle. A minor arc measures less than 180°.
  • perpendicular bisector A line that cuts a segment in half at a right angle. The perpendicular bisector of any chord passes through the center.
  • point of tangency The single point where a tangent meets the circle. The radius to the point of tangency meets the tangent at 90°.
  • secant A line that passes through the circle, meeting it twice. A secant contains a chord.
  • subtend To lie opposite an angle and mark its width. A diameter subtends a right angle at any other point of the circle.
  • tangent A line that meets the circle once and does not cross it. A tangent is perpendicular to the radius drawn to it.
  • tangent circles Two circles that touch at exactly one point. Two coins pushed edge to edge show tangent circles.

Measures and figures 12

  • annulus The flat ring that lies between two concentric circles. A flat washer has the shape of an annulus.
  • arc length The distance along an arc from one end to the other. A semicircle's arc length is half the circumference.
  • area The size of the flat region the circle encloses. A = πr².
  • circumcircle The circle that passes through every corner of a polygon. Every triangle has a circumcircle.
  • circumscribed polygon A polygon whose sides are all tangent to one circle. A square drawn around a circle touches it four times.
  • cyclic quadrilateral A four-sided figure whose corners all lie on one circle. Every rectangle is a cyclic quadrilateral.
  • great circle A circle on a sphere whose center is the sphere's center. The equator is a great circle.
  • incircle The circle inside a polygon that touches every side. Every triangle has an incircle.
  • inscribed polygon A polygon drawn inside a circle with every corner on it. A square can be an inscribed polygon.
  • locus Every point that meets a stated condition, taken together. A circle is the locus of points at one distance from a center.
  • radian The angle at the center cut off by an arc one radius long. A full circle measures 2π radians.
  • unit circle A circle with a radius of 1. Its circumference is 2π.

How this list was compiled: Term list chosen for this site on 2026-10-02. Each meaning is written in our own words and was checked that day against the term's entry in Wiktionary, the free dictionary (https://en.wiktionary.org/), whose text is under the Creative Commons Attribution-ShareAlike license, and, for the terms with no entry of their own (inscribed angle, minor arc, major arc, concentric circles, tangent circles, circumscribed polygon, inscribed polygon), against the articles Circle, Inscribed angle, Circular arc, Annulus (mathematics), Tangent circles, Tangential polygon and Inscribed figure in English Wikipedia (https://en.wikipedia.org/), whose text is under the Creative Commons Attribution-ShareAlike license. The example after each meaning is our own. Licence: own work

How it works

This circle vocabulary worksheet prints twelve terms down the left and their meanings, mixed up, down the right. Three sets cover the parts of a circle, its lines, angles and arcs, and its measures and figures.

Read the full guide

Three sets

Set opens on Parts of a circle: center, radius, diameter, chord, circumference, arc, semicircle, sector, segment, pi and disk. Lines, angles and arcs adds tangent, secant, central angle and inscribed angle. Measures and figures goes on to radian, annulus and circumcircle.

Words only, no drawing

The sheet prints terms and meanings, not a circle to label. Under the tool each term has an example, such as: A chord need not pass through the center. Your own term = meaning lines, typed in the box, replace ours.

  • The third set is high school geometry. A first lesson on circles needs only Parts of a circle.

Questions and answers

What are the vocabulary words for a circle?

The first twelve are circle, center, radius, diameter, chord, circumference, arc, semicircle, sector, segment, pi and disk. A geometry unit adds tangent, secant, central angle, inscribed angle, minor arc and major arc.

What is the difference between a chord and a diameter?

A chord is any segment with both endpoints on the circle. A diameter is a chord that passes through the center, which makes it the longest chord and twice the radius.

What is the difference between a sector and a segment?

A sector is a wedge with its tip at the center, between two radii and an arc. A segment is the region between one chord and the arc it cuts off.

Is there an answer key?

Yes. It prints as a second page: the same sheet with a line drawn from each term to its meaning. See the answers, under More options, shows the same on screen.

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