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Shape vocabulary words for geometry

This list helps students describe flat and solid shapes with precise geometry vocabulary. It covers circles, polygons, triangles, and three-dimensional solids, along with the words used to describe their parts.

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Shape vocabulary words for geometry

30 words
WordMeaningIn a sentenceSave
circlenounA perfectly round, flat shape whose points are all the same distance from its center.The children held hands and formed a circle on the playground.
trianglenounA geometric shape with three straight sides and three angles.The teacher drew a triangle on the board to explain its three angles.
squarenounA flat shape with four equal straight sides and four right angles.He drew a square on the paper and measured each side carefully.
rectanglenounA flat, four-sided shape with four right angles.Draw a rectangle that is six centimeters long and three centimeters wide.
pentagonnounA flat geometric shape with five straight sides and five angles.The students used a ruler to draw a pentagon with five equal sides.
hexagonnounA flat shape with six straight sides and six angles.The honeycomb cells form a repeating pattern of tiny hexagons.
octagonnounA two-dimensional shape with eight straight sides and eight angles.A stop sign is shaped like a regular octagon with equal sides.
polygonnounA closed, flat shape with three or more straight sides.A triangle is a polygon with three sides.
radiusnounA line segment from a circle's center to its boundary, or the length of that segment.The radius of a circle with diameter 12 centimeters is 6 centimeters.
diameternounA line segment across a circle through its center, or the length of that segment.Draw a diameter through the center of the circle.
circumferencenounThe distance around a circle.We wrapped a string around the lid to estimate its circumference.
vertexnounThe point where two or more lines or edges meet, such as the corner of an angle or shape.Each triangle has three vertices, the points where its sides intersect.
edgenounThe outer boundary or line where something ends, or a slight advantage over a rival.She sat carefully on the edge of the cliff to take in the view.
facenounThe front part of the head, from forehead to chin, including the eyes, nose, and mouth.A wide smile spread across his face when he saw the surprise party.
anglenounA figure formed by two rays that start at the same point, or the measure of the turn between them.The two rays form a right angle.
sidenounOne of the flat surfaces of an object, or a position or area to the left or right of something.He leaned against the side of the building to catch his breath.
perimeternounThe total distance around the boundary of a flat shape.The square has sides of 4 centimeters and a perimeter of 16 centimeters.
areanounThe amount of two-dimensional space inside a region or across a surface.A rectangle that is 3 meters by 4 meters has an area of 12 square meters.
spherenounA perfectly round three-dimensional shape in which every point on the surface is the same distance from the center.A basketball is roughly a sphere, though it flattens slightly under pressure.
cubenounA three-dimensional solid shape with six equal square faces.The child stacked wooden cubes to build a small tower.
cylindernounA solid or hollow geometric shape with two parallel circular ends joined by a curved surface.The engineer calculated the volume of the cylinder before ordering the metal pipe.
conenounA solid shape with a circular base that narrows smoothly to a single point.The child's ice cream cone melted faster than she could eat it.
pyramidnounA large monumental structure with a square base and four triangular sides that meet at a point.Tourists from around the world climb the steps near the ancient pyramids of Giza each year.
prismnounA transparent solid, usually glass, with flat sides that bends light and separates it into a spectrum of colors.Sunlight passing through the prism split into a rainbow of colors on the wall.
symmetrynounThe quality of having balanced, matching proportions on either side of a dividing line or point.The butterfly's wings show near-perfect symmetry in their color and pattern.
paralleladjectiveDescribing straight lines in the same plane that never meet, however far they extend.Opposite sides of a rectangle are parallel.
perpendicularadjectivePositioned at an exact right angle, ninety degrees, to another line or surface.The carpenter checked that the wall was perpendicular to the floor before installing shelves.
quadrilateralnounA polygon with exactly four sides and four angles.Squares, rectangles, and trapezoids are all examples of a quadrilateral.
diagonaladjectiveRunning in a straight, slanting direction rather than horizontally or vertically, especially between two opposite corners.The bishop in chess can only move along a diagonal line across the board.
congruentadjectiveHaving exactly the same size and shape, so that one figure matches another perfectly.The two triangles are congruent because their corresponding sides and angles are equal.

2D versus 3D shape words

Shape vocabulary splits into flat, two-dimensional figures and solid, three-dimensional ones. A polygon such as a triangle, pentagon, or hexagon is a flat shape made of straight sides, described using words like vertex, edge, and angle. A 3D shape such as a cube, cylinder, or pyramid has faces and edges too, but it also has volume because it takes up space.

Circle words

A circle has its own special vocabulary. The radius is the distance from the center to the edge, the diameter is the distance across the circle through its center, and the circumference is the distance around the outside. These words come up often in projects that ask students to measure or draw circles accurately.

Frequently asked questions

What is the difference between a polygon and a 3D shape?

A polygon is a flat, two-dimensional shape with straight sides, while a 3D shape has length, width, and height, like a cube or a pyramid.