## AAS

The Angle Angle Side postulate (often abbreviated as AAS) states that if two angles and the non-included side of one triangle are congruent to two angles and the non-included side of another triangle, then these two triangles are congruent.

## Altitude

A line segment from a triangle vertex and perpendicular to the opposite base.

## Annulus

The ring-shaped region bounded by two concentric circles.

## Base

The base of a polygon is the side from which the height is measured.

## Bisector

Line that divides something, such as an angle, in two equal parts.

## Centroid

The point of intersection of the three medians of a triangle. It divides each median in parts of ratio 1 : 2.

## Cevian

A line segment from a triangle vertex to the opposing side.

## Chord

A chord is a line segment connecting two points on a circle. Equal-length chords span equal angles in the centre.

## Circle

All points in a plane that have a fixed distance (radius) from a fixed point (centre).

## Circular arc

Part of a circle’s boundary, characterized by its radius and a certain angle.