segment bisector/midpoint
divides a segment into 2 ≅ segments
angle bisector
divides an angle into 2 ≅ angles
vertical angles/right angles
angles are ≅
complementary angles
2 or more angles whose sum is 90°
supplementary angles
2 or more angles whose sum is 180°
isosceles triangle
a triangle with 2 ≅ legs and base angles
perpendicular lines
form ≅ right angles
parallel lines
lines cut by a transversal form ≅ alternate interior/corresponding angles
median
divides a segment into 2 ≅ segments(meets at the midpoint)
altitude
is perpendicular to the base