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parallel lines

a line in a plane that never intersect

convex

diagonals do not have any points outside the polygon

concave

one or more diagonals have points outside the polgon

diagonal

a line segment, other than a side, that joins two verticles of a polygon

regular polygon

a polygon with all sides and all angles congruent

polygon

a closed plane figure made of the line segments

alternate exterior angles

a pair of non-adjacent exterior angles on opposite sides of the transversal

congruent segments

segments that are equal in length

midpoint

a point that divides a line segment onto two congruent segemts

straight angle

an angle that measures 180

obtuse angle

an angle with a measure greater than 90 and less than 180

acute angle

an angle that measures less that 90

right angle

an angle that measures 90

perpendicular lines

lines that intersects to form right angles

segment bisector

any line ray or segment that intersects a segment at it's midpoint

perpendicular bisector

a line that is perpendicular to a line segment and divides that segments onto 2 congruent parts

congruent angles

angles that have the same size and shape

angle bisector

the ray that divides a given angle onto 2 congruent angles

complementary angles

2 angles whose measures have a sum of 90

supplementary angles

2 angles whose measures have the sum of 180

adjacent angles

2 angles that are in the same plane

vertacile angles

2 congruent angles formed by intersecting lines

transversatle

a line that intersects 2 or more lines at different points

corresponding angles

a pair of non-adjacentangles

alternite interior angles

a pair of non-adjacent interior angles on opposite sides of the transversal