Naming Geometric Objects

Geometry · Axiom Academy

LESSON Naming Geometric Objects Standard notation for points, lines, segments, rays, angles, and planes Each geometric object has a symbol and a standard way to read it aloud. The dots mark named points; arrowheads mean the object extends forever in that direction. A few conventions keep the notation unambiguous. The biggest one: order matters for rays, but not for segments . Points are always named with capital letters: A , B , C , … Lines can be named by two points ( ) or a single lowercase letter ( ). Segments can be named in either order: . Rays must list the endpoint first: starts at A . Angles list the vertex in the middle: in , point B is the vertex. A segment is the same set of points read either way; a ray fixes its starting endpoint. Why the vertex sits in the middle An angle is formed by two rays sharing an endpoint — the vertex . Writing puts that shared point ( B ) between the two outer points, so and name the same angle, but is the shortcut when there's no ambiguity. You can now name every basic geometric object with standard notation — and you know which names depend on order and which don't. Scroll up to revisit any step.

This is the written version of the interactive lesson above. See the full Geometry course.