Geometry Vocabulary Notes

A Point A point is an exact location. Line Line Segment Plane P A line is a set of points that extend without end in opposite directions. A line segment is part of a line or ray. It consists of 2 end points and all points between those end points. A plane is a set of points forming a flat surface that extends without end in all directions. XY XY

XY Ray A ray is a part of a line having one end point and extending in one direction without end. Angle An angle is a geometric figure formed by 2 rays that have a common endpoint. A B C R S T RST Right Angle A right angle is an angle whose measure is ninety degrees. A C B Acute Angle An acute angle is an angle whose measure is greater than zero degrees but less than ninety degrees.

E FG Obtuse Angle An obtuse angle is an angle whose measure is greater than ninety degrees but less than one hundred eighty degrees. XYZ Straight Angle A straight angle is an angle whose measure is one hundred eighty degrees. 50° C E B D 40° DBE andEBC Complementary Angles Complementary angles are two angles whose measures have the sum of ninety degrees 40° 50° A E BC D Supplementary Angles Supplementary angles are two angles whose sum equals one eighty degrees. ABD andDBC

A Intersecting Lines Intersecting lines are lines that cross at exactly one point Vertical Angles Vertical angles are a pair of opposite congruent angles formed by intersecting lines. 1 and3 2 and4 AB D C Adjacent Angles Adjacent angles are angles that share a common side, have the same vertex, but do not overlap. A C B D Perpendicular Lines Perpendicular lines are lines that intersect to form right angles.

DC BA Parallel Lines Parallel lines are lines in a plane that do not intersect.

Triangle Definitions Triangles are defined by their inside and by their outside. When we discuss triangles we must use both the inside and the outside to give an accurate description of a triangle

Inside 53° 90° 37° Right Triangle A right triangle is a triangle containing exactly one right angle. 70° 60°50° Acute Triangle An acute triangle is a triangle in which all three angles are acute. (Remember that acute means less than ninety degrees but more the zero degrees.) 110° 45° 25° Obtuse Triangle An obtuse triangle is a triangle containing one obtuse angle. (Remember that obtuse means more than ninety degrees but less than one hundred eighty degrees.)

Outside 5 m 7 m 6 m Scalene Triangle A scalene triangle is a triangle with no congruent sides. (Remember that congruent means same size and same shape. ) 5 ft 8 ft Isosceles Triangle An isosceles triangle is a triangle with two congruent sides. 10 mm Equilateral Triangle An equilateral triangle is a triangle with three congruent sides and three congruent angles.

Ththththats all Folks!!!