Non-linear writing is writing which made up of marks other than lines, to be distinguished from linear writing.

Cuneiform is probably the earliest non-linear writing. Its symbols are different-shaped impressions, formed by pressing the sharpened end of a reed stylus into moist clay, not scratching the clay in lines as had been done previously.

Arguably, the symbols of Chinese script might be considered non-linear since they are formed of brush strokes, which are not lines of uniform width. However, the essence of the characters can in fact be rendered by plain lines, so this remains an open question. The same argument applies to Egyptian hieroglyphics and Maya hieroglyphics, which are either painted with great detail or carved into stone.

There are several non-linear adaptations of the Roman alphabet, based upon the principles of simple substitution ciphers. There is a one-to-one correspondence between the original linear symbols and the resulting new non-linear symbols. In the case of the Braille alphabet for the blind, the new symbols consist of raised bumps on the writing substrate, which can be paper, metal, plastic or Louis Braille's original leather. In the case of maritime signal flags, the symbols are individual flags with varied coloration.

The pattern of encoded magnetic traces used in modern computers is also a substitution cipher for traditional linear alphabets. Although the magnetic traces may be evanescent, they are still permanent enough to be considered a permanent means of recording speech. Two early encoding schemes were the ASCII and the EBCDIC, and today there are dozens of variations.

There are also impermanent substitution ciphers of the Latin alphabet, namely Morse Code, the alphabetic component of American Sign Language and two varieties of semaphore, one involving flags waved according to specific patterns, and the other involving stationary bars held at different prescribed angles. If 'writing' is defined as a permanent means of recording information, then these systems do not qualify, since the symbols disappear as soon as they are used.