Pairs of angles formed where two lines intersect. These angles are formed by rays pointing in opposite directions, and they are congruent. Vertical angles come in pairs.
The point on a segment that lies exactly halfway from each end of the segment. The distance from the endpoint of a segment to its midpoint is half the length of the whole segment.
a line segment connecting two points on a circle; not "do re mi"
A line segment whose endpoints are both on a circle. Not a collection of musical notes.
Any segment from one point on a circle to another. Despite what you might think, they aren't all that musical.
A postulate which states that given a point not located on a line, exactly one line passes through the point that is parallel to original line.
the bottom part of fractions; in this case when more than one fraction has the same bottom as all the others
A unit of measure for the size of an angle. One full rotation is equal to 360 degrees. A right angle is 90 degrees. One degree equals radians.
angles that share a side
Two angles that share both a side and a vertex. They stick by each other through and through.
Angles that add up to 90°
Two wrongs don't make a right, but two complementary angles do. They're two angles that add up to 90° exactly.
Two angles that add up to 90°. Two wrongs don't make a right, but two complementary angles sure do.
A ray that shares a common vertex with an angle, lies within the interior of that angle, and creates two new angles of equal measure.