Angle Bisector: A line or ray that divides an angle into two equal parts. For example, if the angle is 60 degrees, the angle bisector will split it into two angles of 30 degrees each.

Constructing Bisectors with a Compass: Draw an arc from the vertex to create intersection points. Then, without changing the compass width, draw additional arcs from each point to find the bisector.

Incentre of a Triangle: The incentre is the intersection of the triangle’s angle bisectors, equidistant from all three sides.

Inradius and Incircle: The distance from the incentre to any triangle side is the inradius. Use the incentre and inradius to draw the incircle, touching all sides.