Continuity is defined at different levels, with levels C0, C1, and so on for curves and levels G0, G1, and so on for surfaces and faces. Curves that meet are said to have continuity of C0, or contact continuity. Curves that are tangent have a continuity of C1, or tangent continuity. Curves for which the rate of change of the radius of curvature is the same where they meet have a continuity of C2, also described as curvature continuous. You can use curvature continuous in creating face blend fillets. A loft with side tangency is an example of level G1.