geometry
Geometry vocabulary
Explain side, vertex, face, edge, angle, parallel, perpendicular, symmetry and polygon.
Quick answer
Geometry vocabulary helps you describe and understand shapes and how they fit together in the world around you.Learning outcome
By the end of this page, you will know the names of important parts of shapes and how they relate to each other, so you can describe and compare shapes clearly.Why this matters
Geometry vocabulary helps you talk about shapes in maths, art, building, games, and even when you're just describing what you see. When you know these words, you can understand instructions better, solve puzzles, and describe what you see with more accuracy. Whether you're building with LEGO, drawing a house, or playing with blocks, geometry words help you think and talk about space and shapes clearly.How it works
Let’s explore the words that help us describe shapes. Each shape has parts, and we use special words to talk about these parts. These words help us understand how shapes are built, how they fit together, and how they look. We'll look at: - Side – the straight lines that form a shape - Vertex – the point where two sides meet - Face – a flat surface of a 3D shape - Edge – where two faces meet - Angle – the space between two lines that meet at a point - Parallel – lines that never meet, no matter how far they go - Perpendicular – lines that meet at a right angle (90 degrees) - Symmetry – when one half of a shape is a mirror image of the other half - Polygon – a 2D shape with straight sidesExamples you can see
Let’s look at a few examples of each word. Side: A square has 4 sides. Each side is a straight line. If you trace around the square, you follow 4 sides. Vertex: A triangle has 3 vertices (that’s the plural of vertex). Each vertex is where two sides meet. If you look at a triangle, you can see 3 points where the sides come together. Face: A cube has 6 faces. Each face is a flat square. If you look at a dice, you see 6 flat faces. Edge: A cube has 12 edges. Each edge is where two faces meet. If you run your finger along the edge of a dice, you’ll feel where two faces touch. Angle: A right angle is like the corner of a piece of paper. It’s 90 degrees. If you open a book, the corner makes a right angle. An acute angle is smaller than a right angle, like the tip of a slice of pizza. Parallel: The lines on a ruler are parallel. They never meet, even if you extend them. Perpendicular: The corner of a wall and the floor make a perpendicular line. They meet at a right angle. Symmetry: A butterfly has symmetry. If you fold it in half, both wings match exactly. Polygon: A triangle, square, and pentagon are all polygons. They are 2D shapes with straight sides.Try it as a mini adventure
Imagine you're an explorer on a treasure hunt. You have a map that shows shapes and their parts. Your mission is to find the treasure by understanding the shapes around you. 1st time: Look around your room and find a shape. What are its sides? 2nd time: Find a shape with 3 vertices. What shape is it? 3rd time: Look at a book or a box. How many faces does it have? 4th time: Find two lines that are parallel. What do they look like? 5th time: Find two lines that are perpendicular. What do they look like? 6th time: Draw a shape and check if it has symmetry. 7th time: Name a shape that is a polygon. What makes it a polygon?Common mistakes
Mistake: Thinking that a triangle has 4 sides. Why it happens: Confusing the number of sides with the number of vertices. Fix: Count the straight lines that make the shape. A triangle has 3 sides. Mistake: Thinking that a cube has 8 faces. Why it happens: Mixing up faces and vertices. Fix: A cube has 6 faces, and 8 vertices. You can count them by looking at each flat side. Mistake: Believing that all angles are the same size. Why it happens: Not knowing that angles can be acute, right, or obtuse. Fix: Use a protractor or a right angle (like the corner of a piece of paper) to check angles. Mistake: Thinking that a circle is a polygon. Why it happens: Forgetting that polygons must have straight sides. Fix: A circle has no straight sides, so it is not a polygon.Parent and carer guide
As a parent or carer, you can help by: - Pointing out shapes and their parts in everyday life, like a pizza (circle), a book (rectangle), or a traffic sign (triangle). - Using the words you learn to describe what you see together. - Playing games where you ask your child to find things with certain shapes or parts. - Drawing shapes and asking your child to label the sides, angles, or vertices. - Encouraging your child to think about symmetry in nature, like leaves or butterflies. - Not worrying if they get confused at first – learning geometry vocabulary takes time.Practice questions
- How many sides does a hexagon have?
- What is the name of the point where two sides meet?
- How many faces does a cube have?
- What do we call lines that never meet?
- What is a shape with straight sides called?
- How many vertices does a pentagon have?
- What is the name of a shape with 4 equal sides and 4 right angles?
- What do we call the space between two lines?
- What do we call a shape that can be folded in half and both sides match?
- What is the name of the edge where two faces meet?
- 6
- Vertex
- 6
- Parallel
- Polygon
- 5
- Square
- Angle
- Symmetric
- Edge
FAQ
What is a polygon?
A polygon is a 2D shape with straight sides. Examples include triangles, squares, and pentagons.
What is the difference between a face and an edge?
A face is a flat surface of a 3D shape, like a cube has 6 faces. An edge is where two faces meet, like the edge of a cube where two faces touch.
What does symmetry mean?
Symmetry means one half of a shape is a mirror image of the other half. If you fold it in half, the two sides match exactly.
What is a vertex?
A vertex is a point where two sides meet in a 2D shape. For example, a triangle has 3 vertices.
What is the difference between parallel and perpendicular lines?
Parallel lines never meet, no matter how far they go. Perpendicular lines meet at a right angle (90 degrees).