--- title: "Geometric terms and notation" description: "Use conventional geometric terms and notation to describe, sketch, and draw points, lines, parallel and perpendicular lines, right angles, regular polygons, and reflectively/rotationally symmetric pol" canonical: https://lightmysky.com/learn/mathematics/geometric-terms-and-notation-mt_WtIFJSCQIT source: https://lightmysky.com/learn/mathematics/geometric-terms-and-notation-mt_WtIFJSCQIT.md retrieved: 2026-09-02 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Geometric terms and notation Use conventional geometric terms and notation to describe, sketch, and draw points, lines, parallel and perpendicular lines, right angles, regular polygons, and reflectively/rotationally symmetric polygons Subject: Mathematics · Area: Geometry · Ages 11 to 13 Page: https://lightmysky.com/learn/mathematics/geometric-terms-and-notation-mt_WtIFJSCQIT ## Ready when they can - Use correct notation for line segments (AB), angles (∠ABC), and parallel lines (AB ∥ CD) - Sketch a regular hexagon and describe its rotational and reflective symmetry - Identify and label perpendicular and parallel lines in a given figure using standard symbols ## Lesson: Naming points, lines, and angles Geometry has its own shorthand. Instead of describing a shape in long sentences, you name its points, lines, and angles with letters and symbols. Anyone who knows the shorthand can read your notation and draw the exact same shape. **Example.** Triangle ABC has three corners, named A, B, and C. Its three sides are the segments AB, BC, and CA. The angle at corner B is written ∠ABC. The middle letter always names the vertex, the exact point where the angle opens. Some pairs of lines get their own symbols too. Lines that stay the same distance apart and never meet are parallel, written AB ∥ CD. Lines that cross to form a perfect square corner are perpendicular, written AB ⊥ CD. That square corner is a right angle. In a sketch it gets a small square drawn inside it, not the curved arc you use for every other angle. A reader can then tell at a glance which corner is exactly 90 degrees. *(drawing: A regular hexagon: 6 equal sides, 6 lines of reflective symmetry, and rotational symmetry of order 6.)* A regular polygon has every side the same length and every angle the same size. A regular hexagon has 6 equal sides, so it folds in half 6 different ways: that is 6 lines of reflective symmetry. Turn it about its centre and it lands looking the same 6 times in one full turn, so its rotational symmetry is order 6. **Tip.** When you sketch a figure, let the symbols do the talking: a small square for a right angle, matching arrows for parallel lines, and letters in order for every angle and segment. That way anyone can rebuild your drawing without guessing. **Recap.** Letters name the points, ∠, ∥, and ⊥ describe how lines and angles relate, and a small square always marks a right angle. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Regular and irregular polygons](https://lightmysky.com/learn/mathematics/regular-and-irregular-polygons-mt_8H2kO4k2B9) - [Classifying shapes by properties](https://lightmysky.com/learn/mathematics/classifying-shapes-by-properties-mt_liIW336odh) ## Opens up - [Triangle congruence criteria](https://lightmysky.com/learn/mathematics/triangle-congruence-criteria-mt_167X6Ax8P7) - [Properties of triangles and quadrilaterals](https://lightmysky.com/learn/mathematics/properties-of-triangles-and-quadrilaterals-mt_DNYQLahbfa)