Geometry #1 Vocab Flashcards
Three undefined terms
Point, Line, and Plane. All of geometry is based on these three terms. You can’t prove they exist.
Point
A location. Named with a capital letter.
Line
A straight path of points that is indefinitely long. Named with any two points on the line.
Plane
A flat surface of points that is infinitely large. Named with any three non - collinear points on the plane.
Collinear points
Three or more points on the same line.
Non - Collinear points
Three or more points not on the same line
Ray
Part of a line with one endpoint. Name with endpoint and one “direction” point
Endpoint
A point on the end of a segment or a ray
Segment
Part of a line with two endpoints
Parallel lines
Lines in the same plane that do not intersect
Skew lines
Lines not in the same plane that do not intersect
Parallel planes
Planes that do not intersect
Congruent Segments
Line segments that have the same length
Midpoint
A point that divides a segment into two congruent segments
Angle
A figure formed from two rays that share the same endpoint
Vertex
The common endpoint shared by the two rays of an angle
Acute angle
Angle with a measure less than 90°
Right angle
And angle with a measure equal to 90°
Obtuse angle
An angle with a measure between 90° and 180°
Straight angle
An angle with a measure of 180°
Perpendicular lines
Lines that intersect to form right angles
Complementary angles
Two angles with measures that add up to 90°
Supplementary angles
Two angles with measures the add up to 180°
Angle bisector
Ray that divides an angle into two congruent angles
Adjacent angles
Angles that have a common vertex and side but do not overlap
Vertical angles
The non-adjacent angles that are formed when two lines intersect. Vertical angles are always congruent.
Transversal
A line that intersects with two or more other lines
Triangle
A three sided polygon. Named a triangle using the three vertices. Order does not matter.
Acute triangle
A triangle with all angles less than 90°
Right triangle
A triangle with one right angle
Obtuse triangle
A triangle with one obtuse angle
Scalene triangle
A triangle with no congruent sides
Isosceles triangle
A triangle with at least two congruent sides
Equilateral triangle
Triangle with all sides congruent
Polygon
A closed figure formed by joining segments
Regular polygon
A polygon with all sides congruent and all angles congruent
Diagonal
Hey segment connecting two nonconsecutive vertices in a polygon
Quadrilaterals
Four sides, four angles. Sum of the angles is 360°
Circle
All the points in a plane a given distance from a given point
Radius
A segment with one endpoint at the center of a circle and one endpoint on the circle
Chord
A segment with both end points on the circle
Diameter
A chord that goes through the center of a circle
Arc
Part of a circle
Semicircle
Half of the circle. The ends of a diameter divides the circle into a semicircle.
Circumference
The distance around a circle
