Given a triangle with inner and outer Soddy centers and , respectively, the inner Soddy triangle (respectively, outer Soddy triangle ) is the triangle formed by the points of tangency of the inner (respectively, outer) Soddy circle with the three mutually tangent circles centered at each of the vertices of
These triangles were explicitly mentioned but not named by Oldknow (1996). The name "Soddy triangles" is therefore proposed here for the first time.