Linear dimensions and areas of critical curves of the ellipsoidal NFW lens for five values of the convergence parameter κ_s indicated at the left side. Plotted as a function of ellipticity (bottom axis) and eccentricity (top axis) in the left column are: tangential-critical-curve horizontal (solid green) and vertical (long-dashed green) radii plus maximum vertical extent (short-dashed green); radial-critical-curve horizontal (solid purple) and vertical (long-dashed purple) radii; unit-convergence ellipse semi-minor axis (dashed black); convergence−1/2 ellipse semi-major axis (solid black). The coincidence point of the purple, green, and black dashed curves marks the hyperbolic umbilic; the branching point of the short-dashed from the long-dashed green curve marks the tangential-peanut transition. The right column shows the areas enclosed by the tangential (green) and radial (purple) critical curves plotted as a function of ellipticity and eccentricity.