| Definition | Term |
| The circle formed by the three midpoints of the sides of a trinagle and the three altitudes' feet | |
| The point at which all altitudes intersect | |
| The reflection of a median at the angle bisector that passes through the same vertex | |
| The ratio of the length of the side opposite to an angle to the length of the hypotenuse of a triangle | |
| A segment intersecting the vertex of a side and perpendicular to the opposite side | |
| The circle that touches all three sides of the triangle and is located completely insdie the triangle | |
| A triangle containing a single angle with a measure of >90 degrees | |
| The ratio of the length side adjacent to an angle to the length of the hypotenuse of a triangle | |
| A line intersecting a side's midpoint and perpendicular to that side | |
| Method used to conclude congruence between triangles when given two congruent sides and a congruent included angle | |
| A triangle in which all angle measures are less than 90 degrees | |
| The line through the orthocenter, circumcenter, and centroid | |
| The ratio of the length of the side opposite an angle to the length of the side adjacent to the same angle | |
| A triangle in which all sides and angles are congruent | |