Perpendicular Bisector

This cross is an example of a perpendicular bisector because the longer part intersects the shorter part at the midpoint, and it forms a 90 degree angle.

Median, Altitude

The black line cutting through the base of this flag is an example of a median of a triangle, which is a segment from a vertex to the midpoint of the opposite side. It is also an example of altitude, which is the perpendicular segment from a vertex to opposite side.

Congruent

These two orange slices are congruent. They are the same size and shape.

Simile: The first orangle half is as big as the second orange half.

Legs & Base of Triangle, Hypotenuse

This image contains four right triangles, one on each side of the square with the green dot in the center.

A right triangle is a triangle with a right angle.

Also within the right triangle are two legs and a hypotenuse. The hypotenuse is the side across from the right angle, and the legs are the sides connecting the right angle.

This right triangle is also an isosceles triangle. The hypotenuse is also the base.

Obtuse Triangle

The ruler that cuts through the frame of the door on my lovely art project is an example of an obtuse triangle.

An obtuse triangle is a triangle with one angle that is greater than 90 degrees, and two that are less than 90 degrees.

Isosceles Triangle, Equilateral Triangle, Acute Triangle

This yield sign is an example of an isosceles triangle, an equilateral triangle, and an acute triangle.

An isosceles triangle is a triangle with at least two sides that are equal in length. This triangle has three.

An equilateral triangle is a triangle with sides that are all equal in length, and it also has equal angle measures.

An acute triangle is a triangle with three angles measuring under 90 degrees.

Triangle's Vertex and Sides, Scalene Triangle, Right Triangle

This fancy ruler is an example of a scalene triangle, as well as a right triangle.

A scalene triangle is a triangle with three sides, each of different length.

A right triangle is a triangle with exactly one right angle, as seen in the top angle on this triangle.

This fancy ruler also can be used to point out a vertex of the triangle, which is any of the three red markings, and the sides of the triangle, which are marked by the yellow lines.

The vertex in a triangle is a point in a triangle.

The sides of a triangle are the lines which make up the triangle.

Alternate Interior Angles, Corresponding Angles

The wire to my straightener cuts through the lines at the top and bottom of the counter boarder to form corresponding angles (shown with the red lines), along with alternate interior angles (shown with the yellow lines).

Corresponding angles are angles on the same side of the bisector that cuts though two parallel lines, and on the same side of each of the parallel lines.

Alternate interior angles are angles formed when a bisector cuts through two parallel lines. They are the angles located on the inside of the parallel lines, on opposite sides of the bisector.

Corresponding angles are

Parallel Lines

These stairs have examples of parallel lines on them. In between each step is a line parallel to the next.

Parallel lines are lines that are equidistant at all points and never intersect.

Perpendicular Lines

The wooden lines on this glass window on a cabinet are an example of perpendicular lines.

Perpendicular lines are two lines that intersect to form four 90 degree angles.

Vertical Angles

This calendar contains examples of vertical angles. Where each "X" is, there are two sets of vertcial angles (on each X)

Vertical angles are congruent angles that are across from each other, created by two intersecting lines.

Complimentary Angles

This picture shows an example of complimentary angles. The hour, minute, and second hands all are a part of the complimentary angles, because they add up to 90 degrees.

A complimentary angle is where two angles add to equal 90 degrees.

Supplementary Angles

This picture has an example of supplementary angles in it. The supplementary anlges are circles in red.

The poles are two angles adding to 180 degrees, which is the definition of supplementary angles.

Acute/Obtuse Angle

This picture shows examples of both acute, and obtuse angles. An acute angle can be seen on the black stick's right (our left) arm, where the elbow is the point. An obtuse angle can be seen on his left (our right) arm, where the elbow is also the point.

An acute angle is two lines who meet and form an angle lower than 90 degrees, and an obtuse angle is an angle over 90 degrees.

Right Angle

This "loser" hand motion is an example of a right angle.

A right angle is two lines that meet at a 90 degree angle.

Opposite Rays

This road sign is an example of opposite rays. Imagine that the midde of the arrow is split, and each is a separate ray. This has two rays going in the opposite direction.

Opposite rays are two rays that point in opposite directions, along the same line.

Intersection

These swords are an example of intersection. Each of the dual blades intersects the dual blades from the other sword.

Intersection is when two lines cross, or intersect, one another.

Collinear

In this picture, this man's feet are examples of points on the free-throw line. This is an example of when points are collinear.

Collinear means that there are two or more points on the same line, as seen in this man's feet on the free throw line.

Plane

The road is an example of a plane. It sometimes has points and lines through it, shown with tar, holes, stones, and lines painted on the road.

A plane, however, is a never-ending flat surface with no thickness.

Line

A line appears many times in this piece of paper. The blue lines and the red lines.

A line, however, is an undefined term. It continues perfectly straight forever, and would be off of this paper.

Simile: A line is as straight as the edge of a paper.

Line Segment

This "bone pillow" could be seen as a line segment. It is a line, ending at a point on each end.

A line segment is part of a line, with a point on each end.

Point

This zit is an example of a point.

A point, however, is an undefined term.

Equidistant

The fourth red stripe on the American flag is an equal distance from both the top and bottom red stripes.

Equidistant means "equally distant".