Basic Geometry Vocabulary - Unit 1

2. A measurable part of a line consisting of two endpoints
3. Two angles directly across from each other on intersecting lines. (always congruent)
5. Two lines that intersect at a 90 degree angle (right angle)
6. Points that lie on the same line.
13. An angle with a degree measure of 90.
17. If A, B, and C are collinear points and B is between A and C, then AB + BC = AC
18. Two lines that never intersect.
19. The common endpoint of an angle, where the sides intersect.
22. Two angles that share a common side and vertex.
25. Adjacent angles that are supplementary. Combined, they form a straight line.
26. Two angles that have the same measure.
27. A line or ray that divides an angle into two equal parts.
28. Two angles with measures that sum to 90 degrees.
29. A segment, line or plane that intersects a segment at its midpoint.

1. iF <ABD and <DBC are adjacent, then <ABD + <DBC = <ABC.
4. A line that extends indefinitely in one direction
7. An angle with a degree measure greater than 90.
8. An angle with a degree measure of 180.
9. A line, segment, or ray perpendicular to a segment at its midpoint.
10. The formula used to find the midpoint between two endpoints.
11. Two angles with measures that sum to 180 degrees.
12. The intersection of two rays at at an endpoint.
14. Points that lie on the same plane
15. An angle with a degree measure less than 90
16. The formula used to find the distance between two points on a coordinate plane.
20. A flat surface made up of points and extends indefinitely in all directions.
21. Two segments that have the same length
23. A location with no size or shape
24. Is made up of points with no thickness or width