Alternate Interior Angles

congruent angles created by parallel

Alternate Exterior Angles

Then one of the alternate angles is an exterior angle equal to the other angle which is an opposite interior angle in the triangle.

Regular Polygon

a regular polygon is a polygon that is equiangular (all angles are equal in measure) and equilateral (all sides have the same length). Regular polygons may be convex or star. In the limit, a sequence of regular polygons with an increasing number of sides becomes a circle.

Transversal

A line that intersects two or more parallel lines.

acute triangle

A triangle where all three internal angles are acute (less than 90 degrees).

altitude (of a triangle)

The definition of the altitude of a triangle is a line that extends from one vertex of a triangle perpendicular to the opposite side.

cpctc

Corresponding Parts of Congruent Triangles are Congruent

Line Segment

A line segment is a part of a line that is bounded by two distinct end points, and contains every point
on the line between its end points.

Complementary angle

The Complementary Angles are angle whose measures sum to 90 degrees.

Midpoint

The midpoint is the middle point of a line segment.

angle bisection

An angle bisection divides the angle into two angles with equal measures.

congruent

Being isometric-roughly, the same size and shape.

collinear

It's a property of a set points, specifically,  the property lying on a singal line.

Line

An infinitely-extending one-dimensional figure that has no cuvature.

Plane

Abstract surface which has infinite width and length, zero thickness, and zero curvature.

point

A point is the smallest unit of measure, being a subdivision of the lager pica.

supplementary angle

Either of two angles whose sum is 180.

vertical angles

Each of the pairs of opposite angles made by two intersecting lines.

parallel lines

Two straight lines that do not intersect.

skew lines

Two lines that do not intersect but are not parallel.

straight angle

an angle of 180.

right angle

an angle of  90, as in a corner of a square.

Acute Angle

A angle less then 90 degrees but more than 0 degrees.

Obtuse Angle

A angle between 90 and 180 degress.