1. Median - The middle number (in a sorted list of numbers)
2. Altitude - Generally: another word for height. For a triangle: a line at right angles to a side and going through the opposite corner.
3. Incenter - The center of a triangle's "incircle" ... it is where the "angle bisectors" (lines that split each corner's angle in half) meet.
4. Centroid - The "center of mass".
5. Orthocenter - The point where the three "altitudes" meet. An "altitude" is a line that goes through a vertex and is at right angles to the opposite side.
6. Circumcenter - The center of a triangle's circumcircle. It is where the "perpendicular bisectors" (lines that are at right angles to the midpoint of each side) meet.
7. Concurrent Lines - Three or more lines in a plane or higher-dimensional space are said to be concurrent if they intersect at a single point.
8. Equidistant - The same distance from two other things. A point can be Equidistant from 2 other points when it is always the same distance away from those points.
9. Deductive Reasoning - Is the process of reasoning from one or more general statements (premises) to reach a logically certain conclusion.
10. Inductive Reasoning - Is reasoning in which the premises seek to supply strong evidence for (not absolute proof of) the truth of the conclusion. While the conclusion of a deductive argument is supposed to be certain, the truth of an inductive argument is supposed to be probable, based upon the evidence given
11. Radius - The distance from the center to a vertex (corner point) of a regular polygon.
12. Diameter - A straight line going through the center of a circle connecting two points on the circumference.
13. Tangent - A line that just touches a curve at one point, without cutting across it.
14. Secant - A line that intersects two or more points on a curve. (From the Latin secare "to cut") If it only intersects one