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Point

An exact location

Plane

A flat surface extending in 2 directions without end (name using 3 NON-colinear points)

Space

The set of all points

Line

Points extending in opposite directions without end

Segment

A portion of a line between 2 end points

Ray

A portion of a line with 1 endpoint that extends in 1 direction to infinity

Angle

The intersection of 2 rays

Acute angle

An angle whose measure is less than 90 degrees

Right angle

An angle whose measure equals 90 degrees

Obtuse angle

An angle whose measure is between 90 and 180 degrees

Straight angle

An angle whose measure equals 180 degrees

Collinear

Means points on the same line

Complementary angles

Two angles whose sum is 90 degrees

Supplementary angles

Two angles, of whose sum is 180 degrees

Coplanar

Points in the same plane

Rectangle

a parallelogram with all four sides forming right angles

Midpoint

Point in the middle of a segment

Opposite rays

Rays that are going in opposite directions and share the endpoint

Parallel

Lines in the plane that do not intersect.

Perpendicular

Lines that intersect forming right angles

Skew lines

Lines that are in different planes that do not intersect

Acute triangle

A triangle in which all the angles are less than 90 degrees

Scalene triangle

A triangle with none of the sides being congruent

Isosceles triangle

A triangle with at least 2 that are congruent

Equilateral triangle

A triangle with equal sides

Circle

The set of all points in a plain equal distance from a center point

Congruent

Equal distance

Regular polygon

A polygon with all the angles and sides being congruent

Major arch

An arch whose measure is more than 180 degrees

Semicircle

An arch whose measure equals 180 degrees

Parallelogram

A quadrilateral whose opposite sides are both parallel

Rhombus

A parallelogram with all 4 sides being congruent and forming right angles

Trapezoid

A quadrilateral with 1 pair of opposite sides being parallel

Similar

When a figure is an enlargement or reduction of a original figure

Isometry

When the pre-image and the final image are congruent

Dilation

A similarity transformation (can be a enlargement or a reduction)

Translation

The "shift" of a figure over parallel lines of reflection (orientation is the same)

Rotation

The reflection of a figure over 2 intersecting lines (orientation is the same)

Glide Reflection

The reflection of a figure over at least 3 intersecting lines

Tessellation

A repeated geometric pattern that covers a plane