Parts of triangle?

Answer 1

primary: legs, vertex angle, base.
secondary:
the secondary parts of the triangle

median - a segment whose endpoints are a vertex of the triangle and the midpoint of the opposite side

angle bisector - a segment which bisects an angle and whose endpoints are a vertex of the triangle and a point on the opposite side

altitude - a segment from the vertex of the triangle perpendicular to the line containing the opposite side

perpendicular bisector - a line whose points are equidistant from the endpoints of the given side

incenter - the point of concurrency of the three angle bisectors of the triangle

centroid - the point of concurrency of the three medians of the triangle

orthocenter - the point of concurrency of the three altitudes of the triangle

circumcenter - the point of concurrency of the three perpendicular bisectors of the sides of the triangle