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Basic Geometry Definitions

HSG-CO.A.1
Answer Keys Here

Aligned To Common Core Standard:

High School Congruence - HSG-CO.A.1

Common Terms Used in Geometry - Below, we have discussed a few common geometrical terms that you need to know: POINTS - You may assume point as a simple dot on a piece of paper. In geometry, we define this dot as a point in space or flat surface determining an exact location. It has zero dimensions and is identified with an alphabet or a number. LINES - Lines are used to connecting two points on a piece of paper. The line has one-dimension i.e., a line has one length and no width and height. Lines are perfectly straight and extend in both directions. Like points, we assign alphabets to the line too. To label a line, we select any two points on a line. A set of points that is present on the same line is known as collinear. Pair of lines that intersect at one point is known as intersecting lines. Pair of lines that extends forever without intersecting each other is known as parallel lines. Pair of lines that intersect each other to form a 90 degrees angle is known as perpendicular lines. LINE SEGMENT - Line segments are a part of infinitely extending lines. Line segments connect two endpoints. The two endpoints of the line segment are labeled with alphabets or numbers. RAYS - Ray are lines extending in one direction. Rays have one endpoint, and they extend infinitely in one direction. PLANES - Planes have two dimensions. A plane has a width and length but no height. Planes are flat surfaces extending infinitely on all sides. Every two-dimensional figure is known as a plane figure. The set of lines and points lying on the same plane are termed as coplanar. SPACE - Space is the set of the points having three dimensions; height, width, and length. An infinite number of planes form space. Geometrical shapes/figures in space are known as solids.

Printable Worksheets And Lessons


  • A Circle And Lines Step-by-step Lesson-A circle encases parallel and perpendicular lines. Wow, what possibilities!

  • Guided Lesson - Naming angles, intersecting lines, right angles, and the difference between parallel and perpendicular.

  • Guided Lesson Explanation - This is explained in a more round about away than other sections are worded.

  • Practice Worksheet - I was able to parlay ten questions from two geometric drawings. We focus on the same skills you will find in the standards.

  • Matching Worksheet - Note to self, I forget to add the distance along lines and circles that the standard asks for. Include that in five packs.



Homework Sheets

It's all about calling out lines. Perpendicular versus parallel lines, intersecting lines and naming angles.

  • Homework 1 - Perpendicular lines meet at right angles (90°). Parallel lines are two lines on the same plane that never meet; they are the same distance apart at all points.
  • Homework 2 - One or more lines that meet at a point are known as intersecting lines.
  • Homework 3 - Name the lines that intersect four other lines.



Practice Worksheets

We give you a basic geometric layout and ask you to apply your geometry vocabulary.

  • Practice 1 - Name two right triangles.
  • Practice 2 - Which line segment would be equal to the diameter of the circle?
  • Practice 3 - Angles are named using the points of the angle with the vertex in between.



Math Skill Quizzes

These focus a bit more on naming angles than naming lines.

  • Quiz 1 - Identify parallel lines in the diagram.
  • Quiz 2 - Which line segment would be equal to the radius of circle B?
  • Quiz 3 - Are there any lines that intersect other lines?