Geometry Terms Flashcards

Geometry Terms

• Point: A specific location represented by a dot and typically labeled with a letter.
• Line: An infinite straight path extending in both directions, named using two points on the line.
• Line Segment: A part of a line defined by two endpoints, named after these endpoints.
• Ray: A line segment with one endpoint that extends infinitely in one direction, named starting with the endpoint.
• Plane: An infinite flat surface named by three distinct points within it.
• Intersecting Lines: Lines that cross each other at one or more points.
• Parallel Lines: Lines that remain equidistant and never meet or diverge.
• Perpendicular Lines: Lines that intersect to form right angles (90 degrees).

Angles

• Degrees: Units used for angle measurement.
• Right Angle: An angle measuring exactly 90 degrees.
• Acute Angle: An angle that measures less than 90 degrees; considered 'small'.
• Obtuse Angle: An angle that exceeds 90 degrees; characterized as 'large'.
• Straight Angle: An angle measuring 180 degrees, appearing as a straight line.
• Interior Angle: An angle located inside a shape.
• Exterior Angle: An angle located outside a shape.
• Complementary Angles: Two angles that sum to 90 degrees.
• Supplementary Angles: Two angles that sum to 180 degrees.

Triangles

• Equilateral Triangle: A triangle with all sides of equal length.
• Isosceles Triangle: A triangle with two sides of equal length.
• Scalene Triangle: A triangle with no sides of equal length.
• Right Triangle: A triangle that includes a 90-degree angle.
• Acute Triangle: A triangle with three angles each measuring less than 90 degrees.
• Obtuse Triangle: A triangle containing one angle greater than 90 degrees.

Polygon Basics

• Polygon: A shape with at least three straight sides, with no gaps or curves.
• Quadrilateral: A polygon with four sides.
• Regular Polygon: A polygon with all sides and angles congruent.
• Irregular Polygon: A polygon made up of sides of different lengths and angles.
• Specific Polygon Names:
  • Pentagon: Five sides.
  • Hexagon: Six sides.
  • Heptagon: Seven sides.
  • Octagon: Eight sides.
  • Nonagon: Nine sides.
  • Decagon: Ten sides.
  • Undecagon: Eleven sides.
  • Dodecagon: Twelve sides.

Circles

• Center of a Circle: The point equidistant from all points on the circumference.
• Radius: A line segment from the center to any point on the circle.
• Diameter: A line segment passing through the center, connecting two points on the circle.
• Chord: A line segment connecting two points on the circle, not necessarily passing through the center.
• Central Angle: An angle whose vertex is positioned at the center of the circle.
• Circumference: The total distance around a circle.

Symmetry

• Line Symmetry: Occurs when a shape can be divided along a line such that both halves are congruent.
• Rotational Symmetry: When a shape can be rotated less than 360 degrees and appear unchanged.