If you can fold something along a line of symmetry so that all the points on one side of the line exactly coincide with (or match) all the points on the other side of the line.
What is reflectional symmetry?
100
If something looks the same after you turn it around a point by less than a full circle.
What is rotational symmetry?
100
This is what unit an angle is measured in.
What is degrees?
200
a straight, continuous arrangement of infinitely many points
What is a line?
200
A 90 degree angle
What is a right angle?
200
An angle that measures less than 90 degrees.
What is an acute angle?
200
An angle that measures more than 90 degrees.
What is an obtuse angle?
200
Two rays that share a common endpoint, provided that the two rays are noncollinear.
What is an angle?
300
It has length and width, but no thickness
What is a plane
300
two points called the endpoints of the segment and all the points between them that are collinear with the two points
What is a line segment?
300
The two points at the end of a line segment, arc, etc.
What are endpoints?
300
The two rays of an angle
What are the sides?
300
The common endpoint of the two rays
What is a vertex
400
on the same plane
What is coplanar
400
to divide a segment into two congruent segments
What is bisect?
400
a segment is the point on the segment that is the same distance from both endpoints
What is a midpoint?
400
a line with an arrow at only one end and an endpoint at the other
What is a ray?
400
Number of letters needed to name an angle
3 letters
500
The smallest amount of rotation about the vertex from one ray to the other
What is the measure of an angle?
500
The largest amount of rotation less than 360° between two rays
What is the reflex measure of an angle?
500
Two angles that have equal measures and the same number of degrees.
What are congruent angles
500
A ray that contains the vertex of the angle and divides the angle into two congruent angles
What is an angle bisector?
500
These two tools were the first and only necessary tools to construct in geometry.