It concerns with rays entering the lens obliquely.

A failure of a lens to produce a point image of an object point.

The image formed by lens comes to a sharper focus on curved surface than on  a flat surface.

The outer parts of the image produced by the lens will be magnified either less or more than the center image.

The inability of the lens to focus all colors in the same plane.

The inability of the lens to produce images, sizes of objects with different colors.

Photographic rays passing through the edges of a lens are bent or refracted more sharply than those passing through the central part of the lens, thus they come to focus near the lens than those of the central rays.

When the curving is outward. This is what we call us:

What do we call if the distortion is curving inward?

This is also called as lateral speherical aberration.

  Condition of the lens producing multiple images.

Is a defect in shape not in sharpness.

the relation of the images of the different point are incorrect with respect to one another.

Form of lens defects in which the horizontal and vertical axis are not equally magnified. Inability of the lens to focus both horizontal and vertical lines.