Paraxial electron/ion trajectories in rotationally symmetric fields are analyzed in the Picht space to derive analytical forms of thin lens characteristics such as focal length F, magnification M, and chromatic and spherical aberration coefficients C-c and C-s. Dimensionless forms of T/F, {(C-c/T)/(T/F)}/(L-o/T)(2), and {(C-2/T)/(T/F)}/(L-o/T)(4), which are determined only by the normalized lens-potential distribution, are derived to evaluate the lens. Here, Tis the lens thickness and L-o is the distance from the object to the lens. As to bipotential or unipotential lenses composed of electrodes facing each other symmetrically, it is found that the accelerating mode at V-2/V-1 = a (> 1) and the decelerating mode at V-2/V-1 = 1/a (< 1) have relationships of F-accel = F-decel, C-c,C-accel = C-c,C-decel/a, and C-s,C-accel = C-s,C-decel/a(1/2), where V-1 and V-2 are the 1st and 2nd electrode potentials, respectively. Under constant lens fields, the known M-dependent C, and C, expressions, i.e., C-c = C-c,C- infinity (1 - 1/M)(2) and C-s = C-s,C- infinity (1 - 1/M)(4), are analytically derived also in the present approach.