Geometry Vocabulary Part 1

Geometry

A Branch of mathematics that deals with points, lines, planes and solids and examines their properties.

Point

has no size, length, width, or height. It is represented by a dot and named by a capital letter.

Line

Set of points which has infinite length but not width or height. Is named by a lowercase letter or by any two points on the line.

Plane

Set of points that has infinite length and width but no height. We name a plane with a capital letter

Space

Set of all points.

Collinear Points

Points that lie on the same line.

Noncollinear points

Points that do not lie on the same line.

Coplanar points

Points that lie on the same plane.

Noncoplanar points

Points that do not lie on the same plane

Segment

Part of a line that consists of two points called endpoints and all points between them.

Ray

Is the part of a line that contains an endpoint and all points extending in the other direction.

Congruent Segments

Segments that have the same length.

Bisector of a segment

Line, ray, segment, or plane that divides a segment into two congruent segments

Midpoint of a Segment

A point that divides the segment into two congruent segments

Acute Angle

An Angle whose measure is between 0 degrees and 90 degrees.

Right Angle

An Angle whose measure is 90 degrees.

Obtuse Angle

An Angle whose measure is greater than 90 degrees but less than 180 degrees.

Straight Angle

An angle whose measure is 180 degrees.

Congruent Angles

Angles that have the same measure.

Angle Bisector

A Ray that divides an angle into two congruent adjacent angles.

Triangle

The figure formed by three segments joining three noncollinear points. Each of the three points is a vertex, and the segments are the sides.

Acute Triangle

A Triangle that has all acute angles

Right Triangle

A Triangle with a right angle.

Obtuse Triangle

A Triangle with an obtuse angle

Equiangular Triangule

A Triangle with all angles congruent.

Scalene Triangle

A Triangle with no sides congruent.

Isosceles Triangle

A Triangle with at least two sides congruent.

Equilateral Triangle

A Triangle with all sides congruent.

Adjacent Angles

Two coplanar angles with a common vertex and a common side between them.

Vertical Angles

The non-adjacent angles formed by two intersecting lines.