
Point:
 Exact location
 Ordered pair of coordinates

Parallel lines
two coplanar lines that either have no points in common or are identical

Distance
absolute value of the difference of two coordinates

Convex set:
set in which all segments connecting points of the set lie entirely in the set

counterexample:
situation where the antecedent (if part) is true but the consequent (then part) is false

Converse:
converse of P >Q is Q >P

Midpoint:
point on segment AB where AM = AB

Circle:
set of all points in a plane a certain distance (radius) from a certain point (center)

Union:
Intersection:
 AUB, is the set of elements which are either in A or in B or in both A and B
 AnB, set of elements which are in both A and B

Polygon:
union of three or more segments in the same plane such that each segment intersects exactly two others @ their endpoints

Angle:
union of two rays that have the same endpoint

Zero:
Acute:
Right:
Obtuse:
Straight:
 if and only if m=0^{o}
 " " 0<m<90^{o}
 " " m=90^{o}
 " " 90<m<180^{o}
 " " m=180^{o}

Complementary:
Supplementary:
 M_{1}+M_{2}=90^{o}
 M_{1}+M_{2}=180^{o}

Bisector:
when an angle is split exactly in half on the interior side

Proof:
Sequence of justified conclusions, leading from the antecedent to the consequent.

Slope:
y_{1}y_{2}/x_{1}x_{2}

Perpendicular lines:
Two segments, rays, or lines that form a 90^{o} angle.

